Source file src/time/time.go
1 // Copyright 2009 The Go Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style 3 // license that can be found in the LICENSE file. 4 5 // Package time provides functionality for measuring and displaying time. 6 // 7 // The calendrical calculations always assume a Gregorian calendar, with 8 // no leap seconds. 9 // 10 // # Monotonic Clocks 11 // 12 // Operating systems provide both a “wall clock,” which is subject to 13 // changes for clock synchronization, and a “monotonic clock,” which is 14 // not. The general rule is that the wall clock is for telling time and 15 // the monotonic clock is for measuring time. Rather than split the API, 16 // in this package the Time returned by [time.Now] contains both a wall 17 // clock reading and a monotonic clock reading; later time-telling 18 // operations use the wall clock reading, but later time-measuring 19 // operations, specifically comparisons and subtractions, use the 20 // monotonic clock reading. 21 // 22 // For example, this code always computes a positive elapsed time of 23 // approximately 20 milliseconds, even if the wall clock is changed during 24 // the operation being timed: 25 // 26 // start := time.Now() 27 // ... operation that takes 20 milliseconds ... 28 // t := time.Now() 29 // elapsed := t.Sub(start) 30 // 31 // Other idioms, such as [time.Since](start), [time.Until](deadline), and 32 // time.Now().Before(deadline), are similarly robust against wall clock 33 // resets. 34 // 35 // The rest of this section gives the precise details of how operations 36 // use monotonic clocks, but understanding those details is not required 37 // to use this package. 38 // 39 // The Time returned by time.Now contains a monotonic clock reading. 40 // If Time t has a monotonic clock reading, t.Add adds the same duration to 41 // both the wall clock and monotonic clock readings to compute the result. 42 // Because t.AddDate(y, m, d), t.Round(d), and t.Truncate(d) are wall time 43 // computations, they always strip any monotonic clock reading from their results. 44 // Because t.In, t.Local, and t.UTC are used for their effect on the interpretation 45 // of the wall time, they also strip any monotonic clock reading from their results. 46 // The canonical way to strip a monotonic clock reading is to use t = t.Round(0). 47 // 48 // If Times t and u both contain monotonic clock readings, the operations 49 // t.After(u), t.Before(u), t.Equal(u), t.Compare(u), and t.Sub(u) are carried out 50 // using the monotonic clock readings alone, ignoring the wall clock 51 // readings. If either t or u contains no monotonic clock reading, these 52 // operations fall back to using the wall clock readings. 53 // 54 // On some systems the monotonic clock will stop if the computer goes to sleep. 55 // On such a system, t.Sub(u) may not accurately reflect the actual 56 // time that passed between t and u. The same applies to other functions and 57 // methods that subtract times, such as [Since], [Until], [Time.Before], [Time.After], 58 // [Time.Add], [Time.Equal] and [Time.Compare]. In some cases, you may need to strip 59 // the monotonic clock to get accurate results. 60 // 61 // Because the monotonic clock reading has no meaning outside 62 // the current process, the serialized forms generated by t.GobEncode, 63 // t.MarshalBinary, t.MarshalJSON, and t.MarshalText omit the monotonic 64 // clock reading, and t.Format provides no format for it. Similarly, the 65 // constructors [time.Date], [time.Parse], [time.ParseInLocation], and [time.Unix], 66 // as well as the unmarshalers t.GobDecode, t.UnmarshalBinary. 67 // t.UnmarshalJSON, and t.UnmarshalText always create times with 68 // no monotonic clock reading. 69 // 70 // The monotonic clock reading exists only in [Time] values. It is not 71 // a part of [Duration] values or the Unix times returned by t.Unix and 72 // friends. 73 // 74 // Note that the Go == operator compares not just the time instant but 75 // also the [Location] and the monotonic clock reading. See the 76 // documentation for the Time type for a discussion of equality 77 // testing for Time values. 78 // 79 // For debugging, the result of t.String does include the monotonic 80 // clock reading if present. If t != u because of different monotonic clock readings, 81 // that difference will be visible when printing t.String() and u.String(). 82 // 83 // # Timer Resolution 84 // 85 // [Timer] resolution varies depending on the Go runtime, the operating system 86 // and the underlying hardware. 87 // On Unix, the resolution is ~1ms. 88 // On Windows version 1803 and newer, the resolution is ~0.5ms. 89 // On older Windows versions, the default resolution is ~16ms, but 90 // a higher resolution may be requested using [golang.org/x/sys/windows.TimeBeginPeriod]. 91 package time 92 93 import ( 94 "errors" 95 "math/bits" 96 _ "unsafe" // for go:linkname 97 ) 98 99 // A Time represents an instant in time with nanosecond precision. 100 // 101 // Programs using times should typically store and pass them as values, 102 // not pointers. That is, time variables and struct fields should be of 103 // type [time.Time], not *time.Time. 104 // 105 // A Time value can be used by multiple goroutines simultaneously except 106 // that the methods [Time.GobDecode], [Time.UnmarshalBinary], [Time.UnmarshalJSON] and 107 // [Time.UnmarshalText] are not concurrency-safe. 108 // 109 // Time instants can be compared using the [Time.Before], [Time.After], and [Time.Equal] methods. 110 // The [Time.Sub] method subtracts two instants, producing a [Duration]. 111 // The [Time.Add] method adds a Time and a Duration, producing a Time. 112 // 113 // The zero value of type Time is January 1, year 1, 00:00:00.000000000 UTC. 114 // As this time is unlikely to come up in practice, the [Time.IsZero] method gives 115 // a simple way of detecting a time that has not been initialized explicitly. 116 // 117 // Each time has an associated [Location]. The methods [Time.Local], [Time.UTC], and Time.In return a 118 // Time with a specific Location. Changing the Location of a Time value with 119 // these methods does not change the actual instant it represents, only the time 120 // zone in which to interpret it. 121 // 122 // Representations of a Time value saved by the [Time.GobEncode], [Time.MarshalBinary], [Time.AppendBinary], 123 // [Time.MarshalJSON], [Time.MarshalText] and [Time.AppendText] methods store the [Time.Location]'s offset, 124 // but not the location name. They therefore lose information about Daylight Saving Time. 125 // 126 // In addition to the required “wall clock” reading, a Time may contain an optional 127 // reading of the current process's monotonic clock, to provide additional precision 128 // for comparison or subtraction. 129 // See the “Monotonic Clocks” section in the package documentation for details. 130 // 131 // Note that the Go == operator compares not just the time instant but also the 132 // Location and the monotonic clock reading. Therefore, Time values should not 133 // be used as map or database keys without first guaranteeing that the 134 // identical Location has been set for all values, which can be achieved 135 // through use of the UTC or Local method, and that the monotonic clock reading 136 // has been stripped by setting t = t.Round(0). In general, prefer t.Equal(u) 137 // to t == u, since t.Equal uses the most accurate comparison available and 138 // correctly handles the case when only one of its arguments has a monotonic 139 // clock reading. 140 type Time struct { 141 // wall and ext encode the wall time seconds, wall time nanoseconds, 142 // and optional monotonic clock reading in nanoseconds. 143 // 144 // From high to low bit position, wall encodes a 1-bit flag (hasMonotonic), 145 // a 33-bit seconds field, and a 30-bit wall time nanoseconds field. 146 // The nanoseconds field is in the range [0, 999999999]. 147 // If the hasMonotonic bit is 0, then the 33-bit field must be zero 148 // and the full signed 64-bit wall seconds since Jan 1 year 1 is stored in ext. 149 // If the hasMonotonic bit is 1, then the 33-bit field holds a 33-bit 150 // unsigned wall seconds since Jan 1 year 1885, and ext holds a 151 // signed 64-bit monotonic clock reading, nanoseconds since process start. 152 wall uint64 153 ext int64 154 155 // loc specifies the Location that should be used to 156 // determine the minute, hour, month, day, and year 157 // that correspond to this Time. 158 // The nil location means UTC. 159 // All UTC times are represented with loc==nil, never loc==&utcLoc. 160 loc *Location 161 } 162 163 const ( 164 hasMonotonic = 1 << 63 165 maxWall = wallToInternal + (1<<33 - 1) // year 2157 166 minWall = wallToInternal // year 1885 167 nsecMask = 1<<30 - 1 168 nsecShift = 30 169 ) 170 171 // These helpers for manipulating the wall and monotonic clock readings 172 // take pointer receivers, even when they don't modify the time, 173 // to make them cheaper to call. 174 175 // nsec returns the time's nanoseconds. 176 func (t *Time) nsec() int32 { 177 return int32(t.wall & nsecMask) 178 } 179 180 // sec returns the time's seconds since Jan 1 year 1. 181 func (t *Time) sec() int64 { 182 if t.wall&hasMonotonic != 0 { 183 return wallToInternal + int64(t.wall<<1>>(nsecShift+1)) 184 } 185 return t.ext 186 } 187 188 // unixSec returns the time's seconds since Jan 1 1970 (Unix time). 189 func (t *Time) unixSec() int64 { return t.sec() + internalToUnix } 190 191 // addSec adds d seconds to the time. 192 func (t *Time) addSec(d int64) { 193 if t.wall&hasMonotonic != 0 { 194 sec := int64(t.wall << 1 >> (nsecShift + 1)) 195 dsec := sec + d 196 if 0 <= dsec && dsec <= 1<<33-1 { 197 t.wall = t.wall&nsecMask | uint64(dsec)<<nsecShift | hasMonotonic 198 return 199 } 200 // Wall second now out of range for packed field. 201 // Move to ext. 202 t.stripMono() 203 } 204 205 // Check if the sum of t.ext and d overflows and handle it properly. 206 sum := t.ext + d 207 if (sum > t.ext) == (d > 0) { 208 t.ext = sum 209 } else if d > 0 { 210 t.ext = 1<<63 - 1 211 } else { 212 t.ext = -(1<<63 - 1) 213 } 214 } 215 216 // setLoc sets the location associated with the time. 217 func (t *Time) setLoc(loc *Location) { 218 if loc == &utcLoc { 219 loc = nil 220 } 221 t.stripMono() 222 t.loc = loc 223 } 224 225 // stripMono strips the monotonic clock reading in t. 226 func (t *Time) stripMono() { 227 if t.wall&hasMonotonic != 0 { 228 t.ext = t.sec() 229 t.wall &= nsecMask 230 } 231 } 232 233 // setMono sets the monotonic clock reading in t. 234 // If t cannot hold a monotonic clock reading, 235 // because its wall time is too large, 236 // setMono is a no-op. 237 func (t *Time) setMono(m int64) { 238 if t.wall&hasMonotonic == 0 { 239 sec := t.ext 240 if sec < minWall || maxWall < sec { 241 return 242 } 243 t.wall |= hasMonotonic | uint64(sec-minWall)<<nsecShift 244 } 245 t.ext = m 246 } 247 248 // mono returns t's monotonic clock reading. 249 // It returns 0 for a missing reading. 250 // This function is used only for testing, 251 // so it's OK that technically 0 is a valid 252 // monotonic clock reading as well. 253 func (t *Time) mono() int64 { 254 if t.wall&hasMonotonic == 0 { 255 return 0 256 } 257 return t.ext 258 } 259 260 // IsZero reports whether t represents the zero time instant, 261 // January 1, year 1, 00:00:00 UTC. 262 func (t Time) IsZero() bool { 263 // If hasMonotonic is set in t.wall, then the time can't be before 1885, so it can't be the year 1. 264 // If hasMonotonic is zero, then all the bits in wall other than the nanoseconds field should be 0. 265 // So if there are no nanoseconds then t.wall == 0, and if there are no seconds then t.ext == 0. 266 // This is equivalent to t.sec() == 0 && t.nsec() == 0, but is more efficient. 267 return t.wall == 0 && t.ext == 0 268 } 269 270 // After reports whether the time instant t is after u. 271 func (t Time) After(u Time) bool { 272 if t.wall&u.wall&hasMonotonic != 0 { 273 return t.ext > u.ext 274 } 275 ts := t.sec() 276 us := u.sec() 277 return ts > us || ts == us && t.nsec() > u.nsec() 278 } 279 280 // Before reports whether the time instant t is before u. 281 func (t Time) Before(u Time) bool { 282 if t.wall&u.wall&hasMonotonic != 0 { 283 return t.ext < u.ext 284 } 285 ts := t.sec() 286 us := u.sec() 287 return ts < us || ts == us && t.nsec() < u.nsec() 288 } 289 290 // Compare compares the time instant t with u. If t is before u, it returns -1; 291 // if t is after u, it returns +1; if they're the same, it returns 0. 292 func (t Time) Compare(u Time) int { 293 var tc, uc int64 294 if t.wall&u.wall&hasMonotonic != 0 { 295 tc, uc = t.ext, u.ext 296 } else { 297 tc, uc = t.sec(), u.sec() 298 if tc == uc { 299 tc, uc = int64(t.nsec()), int64(u.nsec()) 300 } 301 } 302 switch { 303 case tc < uc: 304 return -1 305 case tc > uc: 306 return +1 307 } 308 return 0 309 } 310 311 // Equal reports whether t and u represent the same time instant. 312 // Two times can be equal even if they are in different locations. 313 // For example, 6:00 +0200 and 4:00 UTC are Equal. 314 // See the documentation on the Time type for the pitfalls of using == with 315 // Time values; most code should use Equal instead. 316 func (t Time) Equal(u Time) bool { 317 if t.wall&u.wall&hasMonotonic != 0 { 318 return t.ext == u.ext 319 } 320 return t.sec() == u.sec() && t.nsec() == u.nsec() 321 } 322 323 // A Month specifies a month of the year (January = 1, ...). 324 type Month int 325 326 const ( 327 January Month = 1 + iota 328 February 329 March 330 April 331 May 332 June 333 July 334 August 335 September 336 October 337 November 338 December 339 ) 340 341 // String returns the English name of the month ("January", "February", ...). 342 func (m Month) String() string { 343 if January <= m && m <= December { 344 return longMonthNames[m-1] 345 } 346 buf := make([]byte, 20) 347 n := fmtInt(buf, uint64(m)) 348 return "%!Month(" + string(buf[n:]) + ")" 349 } 350 351 // A Weekday specifies a day of the week (Sunday = 0, ...). 352 type Weekday int 353 354 const ( 355 Sunday Weekday = iota 356 Monday 357 Tuesday 358 Wednesday 359 Thursday 360 Friday 361 Saturday 362 ) 363 364 // String returns the English name of the day ("Sunday", "Monday", ...). 365 func (d Weekday) String() string { 366 if Sunday <= d && d <= Saturday { 367 return longDayNames[d] 368 } 369 buf := make([]byte, 20) 370 n := fmtInt(buf, uint64(d)) 371 return "%!Weekday(" + string(buf[n:]) + ")" 372 } 373 374 // Computations on Times 375 // 376 // The zero value for a Time is defined to be 377 // January 1, year 1, 00:00:00.000000000 UTC 378 // which (1) looks like a zero, or as close as you can get in a date 379 // (1-1-1 00:00:00 UTC), (2) is unlikely enough to arise in practice to 380 // be a suitable "not set" sentinel, unlike Jan 1 1970, and (3) has a 381 // non-negative year even in time zones west of UTC, unlike 1-1-0 382 // 00:00:00 UTC, which would be 12-31-(-1) 19:00:00 in New York. 383 // 384 // The zero Time value does not force a specific epoch for the time 385 // representation. For example, to use the Unix epoch internally, we 386 // could define that to distinguish a zero value from Jan 1 1970, that 387 // time would be represented by sec=-1, nsec=1e9. However, it does 388 // suggest a representation, namely using 1-1-1 00:00:00 UTC as the 389 // epoch, and that's what we do. 390 // 391 // The Add and Sub computations are oblivious to the choice of epoch. 392 // 393 // The presentation computations - year, month, minute, and so on - all 394 // rely heavily on division and modulus by positive constants. For 395 // calendrical calculations we want these divisions to round down, even 396 // for negative values, so that the remainder is always positive, but 397 // Go's division (like most hardware division instructions) rounds to 398 // zero. We can still do those computations and then adjust the result 399 // for a negative numerator, but it's annoying to write the adjustment 400 // over and over. Instead, we can change to a different epoch so long 401 // ago that all the times we care about will be positive, and then round 402 // to zero and round down coincide. These presentation routines already 403 // have to add the zone offset, so adding the translation to the 404 // alternate epoch is cheap. For example, having a non-negative time t 405 // means that we can write 406 // 407 // sec = t % 60 408 // 409 // instead of 410 // 411 // sec = t % 60 412 // if sec < 0 { 413 // sec += 60 414 // } 415 // 416 // everywhere. 417 // 418 // The calendar runs on an exact 400 year cycle: a 400-year calendar 419 // printed for 1970-2369 will apply as well to 2370-2769. Even the days 420 // of the week match up. It simplifies date computations to choose the 421 // cycle boundaries so that the exceptional years are always delayed as 422 // long as possible: March 1, year 0 is such a day: 423 // the first leap day (Feb 29) is four years minus one day away, 424 // the first multiple-of-4 year without a Feb 29 is 100 years minus one day away, 425 // and the first multiple-of-100 year with a Feb 29 is 400 years minus one day away. 426 // March 1 year Y for any Y = 0 mod 400 is also such a day. 427 // 428 // Finally, it's convenient if the delta between the Unix epoch and 429 // long-ago epoch is representable by an int64 constant. 430 // 431 // These three considerations—choose an epoch as early as possible, that 432 // starts on March 1 of a year equal to 0 mod 400, and that is no more than 433 // 2⁶³ seconds earlier than 1970—bring us to the year -292277022400. 434 // We refer to this moment as the absolute zero instant, and to times 435 // measured as a uint64 seconds since this year as absolute times. 436 // 437 // Times measured as an int64 seconds since the year 1—the representation 438 // used for Time's sec field—are called internal times. 439 // 440 // Times measured as an int64 seconds since the year 1970 are called Unix 441 // times. 442 // 443 // It is tempting to just use the year 1 as the absolute epoch, defining 444 // that the routines are only valid for years >= 1. However, the 445 // routines would then be invalid when displaying the epoch in time zones 446 // west of UTC, since it is year 0. It doesn't seem tenable to say that 447 // printing the zero time correctly isn't supported in half the time 448 // zones. By comparison, it's reasonable to mishandle some times in 449 // the year -292277022400. 450 // 451 // All this is opaque to clients of the API and can be changed if a 452 // better implementation presents itself. 453 // 454 // The date calculations are implemented using the following clever math from 455 // Cassio Neri and Lorenz Schneider, “Euclidean affine functions and their 456 // application to calendar algorithms,” SP&E 2023. https://doi.org/10.1002/spe.3172 457 // 458 // Define a “calendrical division” (f, f°, f*) to be a triple of functions converting 459 // one time unit into a whole number of larger units and the remainder and back. 460 // For example, in a calendar with no leap years, (d/365, d%365, y*365) is the 461 // calendrical division for days into years: 462 // 463 // (f) year := days/365 464 // (f°) yday := days%365 465 // (f*) days := year*365 (+ yday) 466 // 467 // Note that f* is usually the “easy” function to write: it's the 468 // calendrical multiplication that inverts the more complex division. 469 // 470 // Neri and Schneider prove that when f* takes the form 471 // 472 // f*(n) = (a n + b) / c 473 // 474 // using integer division rounding down with a ≥ c > 0, 475 // which they call a Euclidean affine function or EAF, then: 476 // 477 // f(n) = (c n + c - b - 1) / a 478 // f°(n) = (c n + c - b - 1) % a / c 479 // 480 // This gives a fairly direct calculation for any calendrical division for which 481 // we can write the calendrical multiplication in EAF form. 482 // Because the epoch has been shifted to March 1, all the calendrical 483 // multiplications turn out to be possible to write in EAF form. 484 // When a date is broken into [century, cyear, amonth, mday], 485 // with century, cyear, and mday 0-based, 486 // and amonth 3-based (March = 3, ..., January = 13, February = 14), 487 // the calendrical multiplications written in EAF form are: 488 // 489 // yday = (153 (amonth-3) + 2) / 5 = (153 amonth - 457) / 5 490 // cday = 365 cyear + cyear/4 = 1461 cyear / 4 491 // centurydays = 36524 century + century/4 = 146097 century / 4 492 // days = centurydays + cday + yday + mday. 493 // 494 // We can only handle one periodic cycle per equation, so the year 495 // calculation must be split into [century, cyear], handling both the 496 // 100-year cycle and the 400-year cycle. 497 // 498 // The yday calculation is not obvious but derives from the fact 499 // that the March through January calendar repeats the 5-month 500 // 153-day cycle 31, 30, 31, 30, 31 (we don't care about February 501 // because yday only ever count the days _before_ February 1, 502 // since February is the last month). 503 // 504 // Using the rule for deriving f and f° from f*, these multiplications 505 // convert to these divisions: 506 // 507 // century := (4 days + 3) / 146097 508 // cdays := (4 days + 3) % 146097 / 4 509 // cyear := (4 cdays + 3) / 1461 510 // ayday := (4 cdays + 3) % 1461 / 4 511 // amonth := (5 ayday + 461) / 153 512 // mday := (5 ayday + 461) % 153 / 5 513 // 514 // The a in ayday and amonth stands for absolute (March 1-based) 515 // to distinguish from the standard yday (January 1-based). 516 // 517 // After computing these, we can translate from the March 1 calendar 518 // to the standard January 1 calendar with branch-free math assuming a 519 // branch-free conversion from bool to int 0 or 1, denoted int(b) here: 520 // 521 // isJanFeb := int(yday >= marchThruDecember) 522 // month := amonth - isJanFeb*12 523 // year := century*100 + cyear + isJanFeb 524 // isLeap := int(cyear%4 == 0) & (int(cyear != 0) | int(century%4 == 0)) 525 // day := 1 + mday 526 // yday := 1 + ayday + 31 + 28 + isLeap&^isJanFeb - 365*isJanFeb 527 // 528 // isLeap is the standard leap-year rule, but the split year form 529 // makes the divisions all reduce to binary masking. 530 // Note that day and yday are 1-based, in contrast to mday and ayday. 531 532 // To keep the various units separate, we define integer types 533 // for each. These are never stored in interfaces nor allocated, 534 // so their type information does not appear in Go binaries. 535 const ( 536 secondsPerMinute = 60 537 secondsPerHour = 60 * secondsPerMinute 538 secondsPerDay = 24 * secondsPerHour 539 secondsPerWeek = 7 * secondsPerDay 540 daysPer400Years = 365*400 + 97 541 542 // Days from March 1 through end of year 543 marchThruDecember = 31 + 30 + 31 + 30 + 31 + 31 + 30 + 31 + 30 + 31 544 545 // absoluteYears is the number of years we subtract from internal time to get absolute time. 546 // This value must be 0 mod 400, and it defines the “absolute zero instant” 547 // mentioned in the “Computations on Times” comment above: March 1, -absoluteYears. 548 // Dates before the absolute epoch will not compute correctly, 549 // but otherwise the value can be changed as needed. 550 absoluteYears = 292277022400 551 552 // The year of the zero Time. 553 // Assumed by the unixToInternal computation below. 554 internalYear = 1 555 556 // Offsets to convert between internal and absolute or Unix times. 557 absoluteToInternal int64 = -(absoluteYears*365.2425 + marchThruDecember) * secondsPerDay 558 internalToAbsolute = -absoluteToInternal 559 560 unixToInternal int64 = (1969*365 + 1969/4 - 1969/100 + 1969/400) * secondsPerDay 561 internalToUnix int64 = -unixToInternal 562 563 absoluteToUnix = absoluteToInternal + internalToUnix 564 unixToAbsolute = unixToInternal + internalToAbsolute 565 566 wallToInternal int64 = (1884*365 + 1884/4 - 1884/100 + 1884/400) * secondsPerDay 567 ) 568 569 // An absSeconds counts the number of seconds since the absolute zero instant. 570 type absSeconds uint64 571 572 // An absDays counts the number of days since the absolute zero instant. 573 type absDays uint64 574 575 // An absCentury counts the number of centuries since the absolute zero instant. 576 type absCentury uint64 577 578 // An absCyear counts the number of years since the start of a century. 579 type absCyear int 580 581 // An absYday counts the number of days since the start of a year. 582 // Note that absolute years start on March 1. 583 type absYday int 584 585 // An absMonth counts the number of months since the start of a year. 586 // absMonth=0 denotes March. 587 type absMonth int 588 589 // An absLeap is a single bit (0 or 1) denoting whether a given year is a leap year. 590 type absLeap int 591 592 // An absJanFeb is a single bit (0 or 1) denoting whether a given day falls in January or February. 593 // That is a special case because the absolute years start in March (unlike normal calendar years). 594 type absJanFeb int 595 596 // dateToAbsDays takes a standard year/month/day and returns the 597 // number of days from the absolute epoch to that day. 598 // The days argument can be out of range and in particular can be negative. 599 func dateToAbsDays(year int64, month Month, day int) absDays { 600 // See “Computations on Times” comment above. 601 amonth := uint32(month) 602 janFeb := uint32(0) 603 if amonth < 3 { 604 janFeb = 1 605 } 606 amonth += 12 * janFeb 607 y := uint64(year) - uint64(janFeb) + absoluteYears 608 609 // For amonth is in the range [3,14], we want: 610 // 611 // ayday := (153*amonth - 457) / 5 612 // 613 // (See the “Computations on Times” comment above 614 // as well as Neri and Schneider, section 7.) 615 // 616 // That is equivalent to: 617 // 618 // ayday := (979*amonth - 2919) >> 5 619 // 620 // and the latter form uses a couple fewer instructions, 621 // so use it, saving a few cycles. 622 // See Neri and Schneider, section 8.3 623 // for more about this optimization. 624 // 625 // (Note that there is no saved division, because the compiler 626 // implements / 5 without division in all cases.) 627 ayday := (979*amonth - 2919) >> 5 628 629 century := y / 100 630 cyear := uint32(y % 100) 631 cday := 1461 * cyear / 4 632 centurydays := 146097 * century / 4 633 634 return absDays(centurydays + uint64(int64(cday+ayday)+int64(day)-1)) 635 } 636 637 // days converts absolute seconds to absolute days. 638 func (abs absSeconds) days() absDays { 639 return absDays(abs / secondsPerDay) 640 } 641 642 // split splits days into century, cyear, ayday. 643 func (days absDays) split() (century absCentury, cyear absCyear, ayday absYday) { 644 // See “Computations on Times” comment above. 645 d := 4*uint64(days) + 3 646 century = absCentury(d / 146097) 647 648 // This should be 649 // cday := uint32(d % 146097) / 4 650 // cd := 4*cday + 3 651 // which is to say 652 // cday := uint32(d % 146097) >> 2 653 // cd := cday<<2 + 3 654 // but of course (x>>2<<2)+3 == x|3, 655 // so do that instead. 656 cd := uint32(d%146097) | 3 657 658 // For cdays in the range [0,146097] (100 years), we want: 659 // 660 // cyear := (4 cdays + 3) / 1461 661 // yday := (4 cdays + 3) % 1461 / 4 662 // 663 // (See the “Computations on Times” comment above 664 // as well as Neri and Schneider, section 7.) 665 // 666 // That is equivalent to: 667 // 668 // cyear := (2939745 cdays) >> 32 669 // yday := (2939745 cdays) & 0xFFFFFFFF / 2939745 / 4 670 // 671 // so do that instead, saving a few cycles. 672 // See Neri and Schneider, section 8.3 673 // for more about this optimization. 674 hi, lo := bits.Mul32(2939745, cd) 675 cyear = absCyear(hi) 676 ayday = absYday(lo / 2939745 / 4) 677 return 678 } 679 680 // split splits ayday into absolute month and standard (1-based) day-in-month. 681 func (ayday absYday) split() (m absMonth, mday int) { 682 // See “Computations on Times” comment above. 683 // 684 // For yday in the range [0,366], 685 // 686 // amonth := (5 yday + 461) / 153 687 // mday := (5 yday + 461) % 153 / 5 688 // 689 // is equivalent to: 690 // 691 // amonth = (2141 yday + 197913) >> 16 692 // mday = (2141 yday + 197913) & 0xFFFF / 2141 693 // 694 // so do that instead, saving a few cycles. 695 // See Neri and Schneider, section 8.3. 696 d := 2141*uint32(ayday) + 197913 697 return absMonth(d >> 16), 1 + int((d&0xFFFF)/2141) 698 } 699 700 // janFeb returns 1 if the March 1-based ayday is in January or February, 0 otherwise. 701 func (ayday absYday) janFeb() absJanFeb { 702 // See “Computations on Times” comment above. 703 jf := absJanFeb(0) 704 if ayday >= marchThruDecember { 705 jf = 1 706 } 707 return jf 708 } 709 710 // month returns the standard Month for (m, janFeb) 711 func (m absMonth) month(janFeb absJanFeb) Month { 712 // See “Computations on Times” comment above. 713 return Month(m) - Month(janFeb)*12 714 } 715 716 // leap returns 1 if (century, cyear) is a leap year, 0 otherwise. 717 func (century absCentury) leap(cyear absCyear) absLeap { 718 // See “Computations on Times” comment above. 719 y4ok := 0 720 if cyear%4 == 0 { 721 y4ok = 1 722 } 723 y100ok := 0 724 if cyear != 0 { 725 y100ok = 1 726 } 727 y400ok := 0 728 if century%4 == 0 { 729 y400ok = 1 730 } 731 return absLeap(y4ok & (y100ok | y400ok)) 732 } 733 734 // year returns the standard year for (century, cyear, janFeb). 735 func (century absCentury) year(cyear absCyear, janFeb absJanFeb) int { 736 // See “Computations on Times” comment above. 737 return int(uint64(century)*100-absoluteYears) + int(cyear) + int(janFeb) 738 } 739 740 // yday returns the standard 1-based yday for (ayday, janFeb, leap). 741 func (ayday absYday) yday(janFeb absJanFeb, leap absLeap) int { 742 // See “Computations on Times” comment above. 743 return int(ayday) + (1 + 31 + 28) + int(leap)&^int(janFeb) - 365*int(janFeb) 744 } 745 746 // date converts days into standard year, month, day. 747 func (days absDays) date() (year int, month Month, day int) { 748 century, cyear, ayday := days.split() 749 amonth, day := ayday.split() 750 janFeb := ayday.janFeb() 751 year = century.year(cyear, janFeb) 752 month = amonth.month(janFeb) 753 return 754 } 755 756 // yearYday converts days into the standard year and 1-based yday. 757 func (days absDays) yearYday() (year, yday int) { 758 century, cyear, ayday := days.split() 759 janFeb := ayday.janFeb() 760 year = century.year(cyear, janFeb) 761 yday = ayday.yday(janFeb, century.leap(cyear)) 762 return 763 } 764 765 // absSec returns the time t as an absolute seconds, adjusted by the zone offset. 766 // It is called when computing a presentation property like Month or Hour. 767 // We'd rather call it abs, but there are linknames to abs that make that problematic. 768 // See timeAbs below. 769 func (t Time) absSec() absSeconds { 770 l := t.loc 771 // Avoid function calls when possible. 772 if l == nil || l == &localLoc { 773 l = l.get() 774 } 775 sec := t.unixSec() 776 if l != &utcLoc { 777 if l.cacheZone != nil && l.cacheStart <= sec && sec < l.cacheEnd { 778 sec += int64(l.cacheZone.offset) 779 } else { 780 _, offset, _, _, _ := l.lookup(sec) 781 sec += int64(offset) 782 } 783 } 784 return absSeconds(sec + (unixToInternal + internalToAbsolute)) 785 } 786 787 // locabs is a combination of the Zone and abs methods, 788 // extracting both return values from a single zone lookup. 789 func (t Time) locabs() (name string, offset int, abs absSeconds) { 790 l := t.loc 791 if l == nil || l == &localLoc { 792 l = l.get() 793 } 794 // Avoid function call if we hit the local time cache. 795 sec := t.unixSec() 796 if l != &utcLoc { 797 if l.cacheZone != nil && l.cacheStart <= sec && sec < l.cacheEnd { 798 name = l.cacheZone.name 799 offset = l.cacheZone.offset 800 } else { 801 name, offset, _, _, _ = l.lookup(sec) 802 } 803 sec += int64(offset) 804 } else { 805 name = "UTC" 806 } 807 abs = absSeconds(sec + (unixToInternal + internalToAbsolute)) 808 return 809 } 810 811 // Date returns the year, month, and day in which t occurs. 812 func (t Time) Date() (year int, month Month, day int) { 813 return t.absSec().days().date() 814 } 815 816 // Year returns the year in which t occurs. 817 func (t Time) Year() int { 818 century, cyear, ayday := t.absSec().days().split() 819 janFeb := ayday.janFeb() 820 return century.year(cyear, janFeb) 821 } 822 823 // Month returns the month of the year specified by t. 824 func (t Time) Month() Month { 825 _, _, ayday := t.absSec().days().split() 826 amonth, _ := ayday.split() 827 return amonth.month(ayday.janFeb()) 828 } 829 830 // Day returns the day of the month specified by t. 831 func (t Time) Day() int { 832 _, _, ayday := t.absSec().days().split() 833 _, day := ayday.split() 834 return day 835 } 836 837 // Weekday returns the day of the week specified by t. 838 func (t Time) Weekday() Weekday { 839 return t.absSec().days().weekday() 840 } 841 842 // weekday returns the day of the week specified by days. 843 func (days absDays) weekday() Weekday { 844 // March 1 of the absolute year, like March 1 of 2000, was a Wednesday. 845 return Weekday((uint64(days) + uint64(Wednesday)) % 7) 846 } 847 848 // ISOWeek returns the ISO 8601 year and week number in which t occurs. 849 // Week ranges from 1 to 53. Jan 01 to Jan 03 of year n might belong to 850 // week 52 or 53 of year n-1, and Dec 29 to Dec 31 might belong to week 1 851 // of year n+1. 852 func (t Time) ISOWeek() (year, week int) { 853 // According to the rule that the first calendar week of a calendar year is 854 // the week including the first Thursday of that year, and that the last one is 855 // the week immediately preceding the first calendar week of the next calendar year. 856 // See https://www.iso.org/obp/ui#iso:std:iso:8601:-1:ed-1:v1:en:term:3.1.1.23 for details. 857 858 // weeks start with Monday 859 // Monday Tuesday Wednesday Thursday Friday Saturday Sunday 860 // 1 2 3 4 5 6 7 861 // +3 +2 +1 0 -1 -2 -3 862 // the offset to Thursday 863 days := t.absSec().days() 864 thu := days + absDays(Thursday-((days-1).weekday()+1)) 865 year, yday := thu.yearYday() 866 return year, (yday-1)/7 + 1 867 } 868 869 // Clock returns the hour, minute, and second within the day specified by t. 870 func (t Time) Clock() (hour, min, sec int) { 871 return t.absSec().clock() 872 } 873 874 // clock returns the hour, minute, and second within the day specified by abs. 875 func (abs absSeconds) clock() (hour, min, sec int) { 876 sec = int(abs % secondsPerDay) 877 hour = sec / secondsPerHour 878 sec -= hour * secondsPerHour 879 min = sec / secondsPerMinute 880 sec -= min * secondsPerMinute 881 return 882 } 883 884 // Hour returns the hour within the day specified by t, in the range [0, 23]. 885 func (t Time) Hour() int { 886 return int(t.absSec()%secondsPerDay) / secondsPerHour 887 } 888 889 // Minute returns the minute offset within the hour specified by t, in the range [0, 59]. 890 func (t Time) Minute() int { 891 return int(t.absSec()%secondsPerHour) / secondsPerMinute 892 } 893 894 // Second returns the second offset within the minute specified by t, in the range [0, 59]. 895 func (t Time) Second() int { 896 return int(t.absSec() % secondsPerMinute) 897 } 898 899 // Nanosecond returns the nanosecond offset within the second specified by t, 900 // in the range [0, 999999999]. 901 func (t Time) Nanosecond() int { 902 return int(t.nsec()) 903 } 904 905 // YearDay returns the day of the year specified by t, in the range [1,365] for non-leap years, 906 // and [1,366] in leap years. 907 func (t Time) YearDay() int { 908 _, yday := t.absSec().days().yearYday() 909 return yday 910 } 911 912 // A Duration represents the elapsed time between two instants 913 // as an int64 nanosecond count. The representation limits the 914 // largest representable duration to approximately 290 years. 915 type Duration int64 916 917 const ( 918 minDuration Duration = -1 << 63 919 maxDuration Duration = 1<<63 - 1 920 ) 921 922 // Common durations. There is no definition for units of Day or larger 923 // to avoid confusion across daylight savings time zone transitions. 924 // 925 // To count the number of units in a [Duration], divide: 926 // 927 // second := time.Second 928 // fmt.Print(int64(second/time.Millisecond)) // prints 1000 929 // 930 // To convert an integer number of units to a Duration, multiply: 931 // 932 // seconds := 10 933 // fmt.Print(time.Duration(seconds)*time.Second) // prints 10s 934 const ( 935 Nanosecond Duration = 1 936 Microsecond = 1000 * Nanosecond 937 Millisecond = 1000 * Microsecond 938 Second = 1000 * Millisecond 939 Minute = 60 * Second 940 Hour = 60 * Minute 941 ) 942 943 // String returns a string representing the duration in the form "72h3m0.5s". 944 // Leading zero units are omitted. As a special case, durations less than one 945 // second format use a smaller unit (milli-, micro-, or nanoseconds) to ensure 946 // that the leading digit is non-zero. The zero duration formats as 0s. 947 func (d Duration) String() string { 948 // This is inlinable to take advantage of "function outlining". 949 // Thus, the caller can decide whether a string must be heap allocated. 950 var arr [32]byte 951 n := d.format(&arr) 952 return string(arr[n:]) 953 } 954 955 // format formats the representation of d into the end of buf and 956 // returns the offset of the first character. 957 func (d Duration) format(buf *[32]byte) int { 958 // Largest time is 2540400h10m10.000000000s 959 w := len(buf) 960 961 u := uint64(d) 962 neg := d < 0 963 if neg { 964 u = -u 965 } 966 967 if u < uint64(Second) { 968 // Special case: if duration is smaller than a second, 969 // use smaller units, like 1.2ms 970 var prec int 971 w-- 972 buf[w] = 's' 973 w-- 974 switch { 975 case u == 0: 976 buf[w] = '0' 977 return w 978 case u < uint64(Microsecond): 979 // print nanoseconds 980 prec = 0 981 buf[w] = 'n' 982 case u < uint64(Millisecond): 983 // print microseconds 984 prec = 3 985 // U+00B5 'µ' micro sign == 0xC2 0xB5 986 w-- // Need room for two bytes. 987 copy(buf[w:], "µ") 988 default: 989 // print milliseconds 990 prec = 6 991 buf[w] = 'm' 992 } 993 w, u = fmtFrac(buf[:w], u, prec) 994 w = fmtInt(buf[:w], u) 995 } else { 996 w-- 997 buf[w] = 's' 998 999 w, u = fmtFrac(buf[:w], u, 9) 1000 1001 // u is now integer seconds 1002 w = fmtInt(buf[:w], u%60) 1003 u /= 60 1004 1005 // u is now integer minutes 1006 if u > 0 { 1007 w-- 1008 buf[w] = 'm' 1009 w = fmtInt(buf[:w], u%60) 1010 u /= 60 1011 1012 // u is now integer hours 1013 // Stop at hours because days can be different lengths. 1014 if u > 0 { 1015 w-- 1016 buf[w] = 'h' 1017 w = fmtInt(buf[:w], u) 1018 } 1019 } 1020 } 1021 1022 if neg { 1023 w-- 1024 buf[w] = '-' 1025 } 1026 1027 return w 1028 } 1029 1030 // fmtFrac formats the fraction of v/10**prec (e.g., ".12345") into the 1031 // tail of buf, omitting trailing zeros. It omits the decimal 1032 // point too when the fraction is 0. It returns the index where the 1033 // output bytes begin and the value v/10**prec. 1034 func fmtFrac(buf []byte, v uint64, prec int) (nw int, nv uint64) { 1035 // Omit trailing zeros up to and including decimal point. 1036 w := len(buf) 1037 print := false 1038 for i := 0; i < prec; i++ { 1039 digit := v % 10 1040 print = print || digit != 0 1041 if print { 1042 w-- 1043 buf[w] = byte(digit) + '0' 1044 } 1045 v /= 10 1046 } 1047 if print { 1048 w-- 1049 buf[w] = '.' 1050 } 1051 return w, v 1052 } 1053 1054 // fmtInt formats v into the tail of buf. 1055 // It returns the index where the output begins. 1056 func fmtInt(buf []byte, v uint64) int { 1057 w := len(buf) 1058 if v == 0 { 1059 w-- 1060 buf[w] = '0' 1061 } else { 1062 for v > 0 { 1063 w-- 1064 buf[w] = byte(v%10) + '0' 1065 v /= 10 1066 } 1067 } 1068 return w 1069 } 1070 1071 // Nanoseconds returns the duration as an integer nanosecond count. 1072 func (d Duration) Nanoseconds() int64 { return int64(d) } 1073 1074 // Microseconds returns the duration as an integer microsecond count. 1075 func (d Duration) Microseconds() int64 { return int64(d) / 1e3 } 1076 1077 // Milliseconds returns the duration as an integer millisecond count. 1078 func (d Duration) Milliseconds() int64 { return int64(d) / 1e6 } 1079 1080 // These methods return float64 because the dominant 1081 // use case is for printing a floating point number like 1.5s, and 1082 // a truncation to integer would make them not useful in those cases. 1083 // Splitting the integer and fraction ourselves guarantees that 1084 // converting the returned float64 to an integer rounds the same 1085 // way that a pure integer conversion would have, even in cases 1086 // where, say, float64(d.Nanoseconds())/1e9 would have rounded 1087 // differently. 1088 1089 // Seconds returns the duration as a floating point number of seconds. 1090 func (d Duration) Seconds() float64 { 1091 sec := d / Second 1092 nsec := d % Second 1093 return float64(sec) + float64(nsec)/1e9 1094 } 1095 1096 // Minutes returns the duration as a floating point number of minutes. 1097 func (d Duration) Minutes() float64 { 1098 min := d / Minute 1099 nsec := d % Minute 1100 return float64(min) + float64(nsec)/(60*1e9) 1101 } 1102 1103 // Hours returns the duration as a floating point number of hours. 1104 func (d Duration) Hours() float64 { 1105 hour := d / Hour 1106 nsec := d % Hour 1107 return float64(hour) + float64(nsec)/(60*60*1e9) 1108 } 1109 1110 // Truncate returns the result of rounding d toward zero to a multiple of m. 1111 // If m <= 0, Truncate returns d unchanged. 1112 func (d Duration) Truncate(m Duration) Duration { 1113 if m <= 0 { 1114 return d 1115 } 1116 return d - d%m 1117 } 1118 1119 // lessThanHalf reports whether x+x < y but avoids overflow, 1120 // assuming x and y are both positive (Duration is signed). 1121 func lessThanHalf(x, y Duration) bool { 1122 return uint64(x)+uint64(x) < uint64(y) 1123 } 1124 1125 // Round returns the result of rounding d to the nearest multiple of m. 1126 // The rounding behavior for halfway values is to round away from zero. 1127 // If the result exceeds the maximum (or minimum) 1128 // value that can be stored in a [Duration], 1129 // Round returns the maximum (or minimum) duration. 1130 // If m <= 0, Round returns d unchanged. 1131 func (d Duration) Round(m Duration) Duration { 1132 if m <= 0 { 1133 return d 1134 } 1135 r := d % m 1136 if d < 0 { 1137 r = -r 1138 if lessThanHalf(r, m) { 1139 return d + r 1140 } 1141 if d1 := d - m + r; d1 < d { 1142 return d1 1143 } 1144 return minDuration // overflow 1145 } 1146 if lessThanHalf(r, m) { 1147 return d - r 1148 } 1149 if d1 := d + m - r; d1 > d { 1150 return d1 1151 } 1152 return maxDuration // overflow 1153 } 1154 1155 // Abs returns the absolute value of d. 1156 // As a special case, Duration([math.MinInt64]) is converted to Duration([math.MaxInt64]), 1157 // reducing its magnitude by 1 nanosecond. 1158 func (d Duration) Abs() Duration { 1159 switch { 1160 case d >= 0: 1161 return d 1162 case d == minDuration: 1163 return maxDuration 1164 default: 1165 return -d 1166 } 1167 } 1168 1169 // Add returns the time t+d. 1170 func (t Time) Add(d Duration) Time { 1171 dsec := int64(d / 1e9) 1172 nsec := t.nsec() + int32(d%1e9) 1173 if nsec >= 1e9 { 1174 dsec++ 1175 nsec -= 1e9 1176 } else if nsec < 0 { 1177 dsec-- 1178 nsec += 1e9 1179 } 1180 t.wall = t.wall&^nsecMask | uint64(nsec) // update nsec 1181 t.addSec(dsec) 1182 if t.wall&hasMonotonic != 0 { 1183 te := t.ext + int64(d) 1184 if d < 0 && te > t.ext || d > 0 && te < t.ext { 1185 // Monotonic clock reading now out of range; degrade to wall-only. 1186 t.stripMono() 1187 } else { 1188 t.ext = te 1189 } 1190 } 1191 return t 1192 } 1193 1194 // Sub returns the duration t-u. If the result exceeds the maximum (or minimum) 1195 // value that can be stored in a [Duration], the maximum (or minimum) duration 1196 // will be returned. 1197 // To compute t-d for a duration d, use t.Add(-d). 1198 func (t Time) Sub(u Time) Duration { 1199 if t.wall&u.wall&hasMonotonic != 0 { 1200 return subMono(t.ext, u.ext) 1201 } 1202 d := Duration(t.sec()-u.sec())*Second + Duration(t.nsec()-u.nsec()) 1203 // Check for overflow or underflow. 1204 switch { 1205 case u.Add(d).Equal(t): 1206 return d // d is correct 1207 case t.Before(u): 1208 return minDuration // t - u is negative out of range 1209 default: 1210 return maxDuration // t - u is positive out of range 1211 } 1212 } 1213 1214 func subMono(t, u int64) Duration { 1215 d := Duration(t - u) 1216 if d < 0 && t > u { 1217 return maxDuration // t - u is positive out of range 1218 } 1219 if d > 0 && t < u { 1220 return minDuration // t - u is negative out of range 1221 } 1222 return d 1223 } 1224 1225 // Since returns the time elapsed since t. 1226 // It is shorthand for time.Now().Sub(t). 1227 func Since(t Time) Duration { 1228 if t.wall&hasMonotonic != 0 && !runtimeIsBubbled() { 1229 // Common case optimization: if t has monotonic time, then Sub will use only it. 1230 return subMono(runtimeNano()-startNano, t.ext) 1231 } 1232 return Now().Sub(t) 1233 } 1234 1235 // Until returns the duration until t. 1236 // It is shorthand for t.Sub(time.Now()). 1237 func Until(t Time) Duration { 1238 if t.wall&hasMonotonic != 0 && !runtimeIsBubbled() { 1239 // Common case optimization: if t has monotonic time, then Sub will use only it. 1240 return subMono(t.ext, runtimeNano()-startNano) 1241 } 1242 return t.Sub(Now()) 1243 } 1244 1245 // AddDate returns the time corresponding to adding the 1246 // given number of years, months, and days to t. 1247 // For example, AddDate(-1, 2, 3) applied to January 1, 2011 1248 // returns March 4, 2010. 1249 // 1250 // Note that dates are fundamentally coupled to timezones, and calendrical 1251 // periods like days don't have fixed durations. AddDate uses the Location of 1252 // the Time value to determine these durations. That means that the same 1253 // AddDate arguments can produce a different shift in absolute time depending on 1254 // the base Time value and its Location. For example, AddDate(0, 0, 1) applied 1255 // to 12:00 on March 27 always returns 12:00 on March 28. At some locations and 1256 // in some years this is a 24 hour shift. In others it's a 23 hour shift due to 1257 // daylight savings time transitions. 1258 // 1259 // AddDate normalizes its result in the same way that Date does, 1260 // so, for example, adding one month to October 31 yields 1261 // December 1, the normalized form for November 31. 1262 func (t Time) AddDate(years int, months int, days int) Time { 1263 year, month, day := t.Date() 1264 hour, min, sec := t.Clock() 1265 return Date(year+years, month+Month(months), day+days, hour, min, sec, int(t.nsec()), t.Location()) 1266 } 1267 1268 // daysBefore returns the number of days in a non-leap year before month m. 1269 // daysBefore(December+1) returns 365. 1270 func daysBefore(m Month) int { 1271 adj := 0 1272 if m >= March { 1273 adj = -2 1274 } 1275 1276 // With the -2 adjustment after February, 1277 // we need to compute the running sum of: 1278 // 0 31 30 31 30 31 30 31 31 30 31 30 31 1279 // which is: 1280 // 0 31 61 92 122 153 183 214 245 275 306 336 367 1281 // This is almost exactly 367/12×(m-1) except for the 1282 // occasonal off-by-one suggesting there may be an 1283 // integer approximation of the form (a×m + b)/c. 1284 // A brute force search over small a, b, c finds that 1285 // (214×m - 211) / 7 computes the function perfectly. 1286 return (214*int(m)-211)/7 + adj 1287 } 1288 1289 func daysIn(m Month, year int) int { 1290 if m == February { 1291 if isLeap(year) { 1292 return 29 1293 } 1294 return 28 1295 } 1296 // With the special case of February eliminated, the pattern is 1297 // 31 30 31 30 31 30 31 31 30 31 30 31 1298 // Adding m&1 produces the basic alternation; 1299 // adding (m>>3)&1 inverts the alternation starting in August. 1300 return 30 + int((m+m>>3)&1) 1301 } 1302 1303 // Provided by package runtime. 1304 // 1305 // now returns the current real time, and is superseded by runtimeNow which returns 1306 // the fake synctest clock when appropriate. 1307 // 1308 // now should be an internal detail, 1309 // but widely used packages access it using linkname. 1310 // Notable members of the hall of shame include: 1311 // - gitee.com/quant1x/gox 1312 // - github.com/phuslu/log 1313 // - github.com/sethvargo/go-limiter 1314 // - github.com/ulule/limiter/v3 1315 // 1316 // Do not remove or change the type signature. 1317 // See go.dev/issue/67401. 1318 func now() (sec int64, nsec int32, mono int64) 1319 1320 // runtimeNow returns the current time. 1321 // When called within a synctest.Run bubble, it returns the group's fake clock. 1322 // 1323 //go:linkname runtimeNow 1324 func runtimeNow() (sec int64, nsec int32, mono int64) 1325 1326 // runtimeNano returns the current value of the runtime clock in nanoseconds. 1327 // When called within a synctest.Run bubble, it returns the group's fake clock. 1328 // 1329 //go:linkname runtimeNano 1330 func runtimeNano() int64 1331 1332 //go:linkname runtimeIsBubbled 1333 func runtimeIsBubbled() bool 1334 1335 // Monotonic times are reported as offsets from startNano. 1336 // We initialize startNano to runtimeNano() - 1 so that on systems where 1337 // monotonic time resolution is fairly low (e.g. Windows 2008 1338 // which appears to have a default resolution of 15ms), 1339 // we avoid ever reporting a monotonic time of 0. 1340 // (Callers may want to use 0 as "time not set".) 1341 var startNano int64 = runtimeNano() - 1 1342 1343 // x/tools uses a linkname of time.Now in its tests. No harm done. 1344 //go:linkname Now 1345 1346 // Now returns the current local time. 1347 func Now() Time { 1348 sec, nsec, mono := runtimeNow() 1349 if mono == 0 { 1350 return Time{uint64(nsec), sec + unixToInternal, Local} 1351 } 1352 mono -= startNano 1353 sec += unixToInternal - minWall 1354 if uint64(sec)>>33 != 0 { 1355 // Seconds field overflowed the 33 bits available when 1356 // storing a monotonic time. This will be true after 1357 // March 16, 2157. 1358 return Time{uint64(nsec), sec + minWall, Local} 1359 } 1360 return Time{hasMonotonic | uint64(sec)<<nsecShift | uint64(nsec), mono, Local} 1361 } 1362 1363 func unixTime(sec int64, nsec int32) Time { 1364 return Time{uint64(nsec), sec + unixToInternal, Local} 1365 } 1366 1367 // UTC returns t with the location set to UTC. 1368 func (t Time) UTC() Time { 1369 t.setLoc(&utcLoc) 1370 return t 1371 } 1372 1373 // Local returns t with the location set to local time. 1374 func (t Time) Local() Time { 1375 t.setLoc(Local) 1376 return t 1377 } 1378 1379 // In returns a copy of t representing the same time instant, but 1380 // with the copy's location information set to loc for display 1381 // purposes. 1382 // 1383 // In panics if loc is nil. 1384 func (t Time) In(loc *Location) Time { 1385 if loc == nil { 1386 panic("time: missing Location in call to Time.In") 1387 } 1388 t.setLoc(loc) 1389 return t 1390 } 1391 1392 // Location returns the time zone information associated with t. 1393 func (t Time) Location() *Location { 1394 l := t.loc 1395 if l == nil { 1396 l = UTC 1397 } 1398 return l 1399 } 1400 1401 // Zone computes the time zone in effect at time t, returning the abbreviated 1402 // name of the zone (such as "CET") and its offset in seconds east of UTC. 1403 func (t Time) Zone() (name string, offset int) { 1404 name, offset, _, _, _ = t.loc.lookup(t.unixSec()) 1405 return 1406 } 1407 1408 // ZoneBounds returns the bounds of the time zone in effect at time t. 1409 // The zone begins at start and the next zone begins at end. 1410 // If the zone begins at the beginning of time, start will be returned as a zero Time. 1411 // If the zone goes on forever, end will be returned as a zero Time. 1412 // The Location of the returned times will be the same as t. 1413 func (t Time) ZoneBounds() (start, end Time) { 1414 _, _, startSec, endSec, _ := t.loc.lookup(t.unixSec()) 1415 if startSec != alpha { 1416 start = unixTime(startSec, 0) 1417 start.setLoc(t.loc) 1418 } 1419 if endSec != omega { 1420 end = unixTime(endSec, 0) 1421 end.setLoc(t.loc) 1422 } 1423 return 1424 } 1425 1426 // Unix returns t as a Unix time, the number of seconds elapsed 1427 // since January 1, 1970 UTC. The result does not depend on the 1428 // location associated with t. 1429 // Unix-like operating systems often record time as a 32-bit 1430 // count of seconds, but since the method here returns a 64-bit 1431 // value it is valid for billions of years into the past or future. 1432 func (t Time) Unix() int64 { 1433 return t.unixSec() 1434 } 1435 1436 // UnixMilli returns t as a Unix time, the number of milliseconds elapsed since 1437 // January 1, 1970 UTC. The result is undefined if the Unix time in 1438 // milliseconds cannot be represented by an int64 (a date more than 292 million 1439 // years before or after 1970). The result does not depend on the 1440 // location associated with t. 1441 func (t Time) UnixMilli() int64 { 1442 return t.unixSec()*1e3 + int64(t.nsec())/1e6 1443 } 1444 1445 // UnixMicro returns t as a Unix time, the number of microseconds elapsed since 1446 // January 1, 1970 UTC. The result is undefined if the Unix time in 1447 // microseconds cannot be represented by an int64 (a date before year -290307 or 1448 // after year 294246). The result does not depend on the location associated 1449 // with t. 1450 func (t Time) UnixMicro() int64 { 1451 return t.unixSec()*1e6 + int64(t.nsec())/1e3 1452 } 1453 1454 // UnixNano returns t as a Unix time, the number of nanoseconds elapsed 1455 // since January 1, 1970 UTC. The result is undefined if the Unix time 1456 // in nanoseconds cannot be represented by an int64 (a date before the year 1457 // 1678 or after 2262). Note that this means the result of calling UnixNano 1458 // on the zero Time is undefined. The result does not depend on the 1459 // location associated with t. 1460 func (t Time) UnixNano() int64 { 1461 return (t.unixSec())*1e9 + int64(t.nsec()) 1462 } 1463 1464 const ( 1465 timeBinaryVersionV1 byte = iota + 1 // For general situation 1466 timeBinaryVersionV2 // For LMT only 1467 ) 1468 1469 // AppendBinary implements the [encoding.BinaryAppender] interface. 1470 func (t Time) AppendBinary(b []byte) ([]byte, error) { 1471 var offsetMin int16 // minutes east of UTC. -1 is UTC. 1472 var offsetSec int8 1473 version := timeBinaryVersionV1 1474 1475 if t.Location() == UTC { 1476 offsetMin = -1 1477 } else { 1478 _, offset := t.Zone() 1479 if offset%60 != 0 { 1480 version = timeBinaryVersionV2 1481 offsetSec = int8(offset % 60) 1482 } 1483 1484 offset /= 60 1485 if offset < -32768 || offset == -1 || offset > 32767 { 1486 return b, errors.New("Time.MarshalBinary: unexpected zone offset") 1487 } 1488 offsetMin = int16(offset) 1489 } 1490 1491 sec := t.sec() 1492 nsec := t.nsec() 1493 b = append(b, 1494 version, // byte 0 : version 1495 byte(sec>>56), // bytes 1-8: seconds 1496 byte(sec>>48), 1497 byte(sec>>40), 1498 byte(sec>>32), 1499 byte(sec>>24), 1500 byte(sec>>16), 1501 byte(sec>>8), 1502 byte(sec), 1503 byte(nsec>>24), // bytes 9-12: nanoseconds 1504 byte(nsec>>16), 1505 byte(nsec>>8), 1506 byte(nsec), 1507 byte(offsetMin>>8), // bytes 13-14: zone offset in minutes 1508 byte(offsetMin), 1509 ) 1510 if version == timeBinaryVersionV2 { 1511 b = append(b, byte(offsetSec)) 1512 } 1513 return b, nil 1514 } 1515 1516 // MarshalBinary implements the [encoding.BinaryMarshaler] interface. 1517 func (t Time) MarshalBinary() ([]byte, error) { 1518 b, err := t.AppendBinary(make([]byte, 0, 16)) 1519 if err != nil { 1520 return nil, err 1521 } 1522 return b, nil 1523 } 1524 1525 // UnmarshalBinary implements the [encoding.BinaryUnmarshaler] interface. 1526 func (t *Time) UnmarshalBinary(data []byte) error { 1527 buf := data 1528 if len(buf) == 0 { 1529 return errors.New("Time.UnmarshalBinary: no data") 1530 } 1531 1532 version := buf[0] 1533 if version != timeBinaryVersionV1 && version != timeBinaryVersionV2 { 1534 return errors.New("Time.UnmarshalBinary: unsupported version") 1535 } 1536 1537 wantLen := /*version*/ 1 + /*sec*/ 8 + /*nsec*/ 4 + /*zone offset*/ 2 1538 if version == timeBinaryVersionV2 { 1539 wantLen++ 1540 } 1541 if len(buf) != wantLen { 1542 return errors.New("Time.UnmarshalBinary: invalid length") 1543 } 1544 1545 buf = buf[1:] 1546 sec := int64(buf[7]) | int64(buf[6])<<8 | int64(buf[5])<<16 | int64(buf[4])<<24 | 1547 int64(buf[3])<<32 | int64(buf[2])<<40 | int64(buf[1])<<48 | int64(buf[0])<<56 1548 1549 buf = buf[8:] 1550 nsec := int32(buf[3]) | int32(buf[2])<<8 | int32(buf[1])<<16 | int32(buf[0])<<24 1551 1552 buf = buf[4:] 1553 offset := int(int16(buf[1])|int16(buf[0])<<8) * 60 1554 if version == timeBinaryVersionV2 { 1555 offset += int(buf[2]) 1556 } 1557 1558 *t = Time{} 1559 t.wall = uint64(nsec) 1560 t.ext = sec 1561 1562 if offset == -1*60 { 1563 t.setLoc(&utcLoc) 1564 } else if _, localoff, _, _, _ := Local.lookup(t.unixSec()); offset == localoff { 1565 t.setLoc(Local) 1566 } else { 1567 t.setLoc(FixedZone("", offset)) 1568 } 1569 1570 return nil 1571 } 1572 1573 // TODO(rsc): Remove GobEncoder, GobDecoder, MarshalJSON, UnmarshalJSON in Go 2. 1574 // The same semantics will be provided by the generic MarshalBinary, MarshalText, 1575 // UnmarshalBinary, UnmarshalText. 1576 1577 // GobEncode implements the gob.GobEncoder interface. 1578 func (t Time) GobEncode() ([]byte, error) { 1579 return t.MarshalBinary() 1580 } 1581 1582 // GobDecode implements the gob.GobDecoder interface. 1583 func (t *Time) GobDecode(data []byte) error { 1584 return t.UnmarshalBinary(data) 1585 } 1586 1587 // MarshalJSON implements the [encoding/json.Marshaler] interface. 1588 // The time is a quoted string in the RFC 3339 format with sub-second precision. 1589 // If the timestamp cannot be represented as valid RFC 3339 1590 // (e.g., the year is out of range), then an error is reported. 1591 func (t Time) MarshalJSON() ([]byte, error) { 1592 b := make([]byte, 0, len(RFC3339Nano)+len(`""`)) 1593 b = append(b, '"') 1594 b, err := t.appendStrictRFC3339(b) 1595 b = append(b, '"') 1596 if err != nil { 1597 return nil, errors.New("Time.MarshalJSON: " + err.Error()) 1598 } 1599 return b, nil 1600 } 1601 1602 // UnmarshalJSON implements the [encoding/json.Unmarshaler] interface. 1603 // The time must be a quoted string in the RFC 3339 format. 1604 func (t *Time) UnmarshalJSON(data []byte) error { 1605 if string(data) == "null" { 1606 return nil 1607 } 1608 // TODO(https://go.dev/issue/47353): Properly unescape a JSON string. 1609 if len(data) < 2 || data[0] != '"' || data[len(data)-1] != '"' { 1610 return errors.New("Time.UnmarshalJSON: input is not a JSON string") 1611 } 1612 data = data[len(`"`) : len(data)-len(`"`)] 1613 var err error 1614 *t, err = parseStrictRFC3339(data) 1615 return err 1616 } 1617 1618 func (t Time) appendTo(b []byte, errPrefix string) ([]byte, error) { 1619 b, err := t.appendStrictRFC3339(b) 1620 if err != nil { 1621 return nil, errors.New(errPrefix + err.Error()) 1622 } 1623 return b, nil 1624 } 1625 1626 // AppendText implements the [encoding.TextAppender] interface. 1627 // The time is formatted in RFC 3339 format with sub-second precision. 1628 // If the timestamp cannot be represented as valid RFC 3339 1629 // (e.g., the year is out of range), then an error is returned. 1630 func (t Time) AppendText(b []byte) ([]byte, error) { 1631 return t.appendTo(b, "Time.AppendText: ") 1632 } 1633 1634 // MarshalText implements the [encoding.TextMarshaler] interface. The output 1635 // matches that of calling the [Time.AppendText] method. 1636 // 1637 // See [Time.AppendText] for more information. 1638 func (t Time) MarshalText() ([]byte, error) { 1639 return t.appendTo(make([]byte, 0, len(RFC3339Nano)), "Time.MarshalText: ") 1640 } 1641 1642 // UnmarshalText implements the [encoding.TextUnmarshaler] interface. 1643 // The time must be in the RFC 3339 format. 1644 func (t *Time) UnmarshalText(data []byte) error { 1645 var err error 1646 *t, err = parseStrictRFC3339(data) 1647 return err 1648 } 1649 1650 // Unix returns the local Time corresponding to the given Unix time, 1651 // sec seconds and nsec nanoseconds since January 1, 1970 UTC. 1652 // It is valid to pass nsec outside the range [0, 999999999]. 1653 // Not all sec values have a corresponding time value. One such 1654 // value is 1<<63-1 (the largest int64 value). 1655 func Unix(sec int64, nsec int64) Time { 1656 if nsec < 0 || nsec >= 1e9 { 1657 n := nsec / 1e9 1658 sec += n 1659 nsec -= n * 1e9 1660 if nsec < 0 { 1661 nsec += 1e9 1662 sec-- 1663 } 1664 } 1665 return unixTime(sec, int32(nsec)) 1666 } 1667 1668 // UnixMilli returns the local Time corresponding to the given Unix time, 1669 // msec milliseconds since January 1, 1970 UTC. 1670 func UnixMilli(msec int64) Time { 1671 return Unix(msec/1e3, (msec%1e3)*1e6) 1672 } 1673 1674 // UnixMicro returns the local Time corresponding to the given Unix time, 1675 // usec microseconds since January 1, 1970 UTC. 1676 func UnixMicro(usec int64) Time { 1677 return Unix(usec/1e6, (usec%1e6)*1e3) 1678 } 1679 1680 // IsDST reports whether the time in the configured location is in Daylight Savings Time. 1681 func (t Time) IsDST() bool { 1682 _, _, _, _, isDST := t.loc.lookup(t.Unix()) 1683 return isDST 1684 } 1685 1686 func isLeap(year int) bool { 1687 // year%4 == 0 && (year%100 != 0 || year%400 == 0) 1688 // Bottom 2 bits must be clear. 1689 // For multiples of 25, bottom 4 bits must be clear. 1690 // Thanks to Cassio Neri for this trick. 1691 mask := 0xf 1692 if year%25 != 0 { 1693 mask = 3 1694 } 1695 return year&mask == 0 1696 } 1697 1698 // norm returns nhi, nlo such that 1699 // 1700 // hi * base + lo == nhi * base + nlo 1701 // 0 <= nlo < base 1702 func norm(hi, lo, base int) (nhi, nlo int) { 1703 if lo < 0 { 1704 n := (-lo-1)/base + 1 1705 hi -= n 1706 lo += n * base 1707 } 1708 if lo >= base { 1709 n := lo / base 1710 hi += n 1711 lo -= n * base 1712 } 1713 return hi, lo 1714 } 1715 1716 // Date returns the Time corresponding to 1717 // 1718 // yyyy-mm-dd hh:mm:ss + nsec nanoseconds 1719 // 1720 // in the appropriate zone for that time in the given location. 1721 // 1722 // The month, day, hour, min, sec, and nsec values may be outside 1723 // their usual ranges and will be normalized during the conversion. 1724 // For example, October 32 converts to November 1. 1725 // 1726 // A daylight savings time transition skips or repeats times. 1727 // For example, in the United States, March 13, 2011 2:15am never occurred, 1728 // while November 6, 2011 1:15am occurred twice. In such cases, the 1729 // choice of time zone, and therefore the time, is not well-defined. 1730 // Date returns a time that is correct in one of the two zones involved 1731 // in the transition, but it does not guarantee which. 1732 // 1733 // Date panics if loc is nil. 1734 func Date(year int, month Month, day, hour, min, sec, nsec int, loc *Location) Time { 1735 if loc == nil { 1736 panic("time: missing Location in call to Date") 1737 } 1738 1739 // Normalize month, overflowing into year. 1740 m := int(month) - 1 1741 year, m = norm(year, m, 12) 1742 month = Month(m) + 1 1743 1744 // Normalize nsec, sec, min, hour, overflowing into day. 1745 sec, nsec = norm(sec, nsec, 1e9) 1746 min, sec = norm(min, sec, 60) 1747 hour, min = norm(hour, min, 60) 1748 day, hour = norm(day, hour, 24) 1749 1750 // Convert to absolute time and then Unix time. 1751 unix := int64(dateToAbsDays(int64(year), month, day))*secondsPerDay + 1752 int64(hour*secondsPerHour+min*secondsPerMinute+sec) + 1753 absoluteToUnix 1754 1755 // Look for zone offset for expected time, so we can adjust to UTC. 1756 // The lookup function expects UTC, so first we pass unix in the 1757 // hope that it will not be too close to a zone transition, 1758 // and then adjust if it is. 1759 _, offset, start, end, _ := loc.lookup(unix) 1760 if offset != 0 { 1761 utc := unix - int64(offset) 1762 // If utc is valid for the time zone we found, then we have the right offset. 1763 // If not, we get the correct offset by looking up utc in the location. 1764 if utc < start || utc >= end { 1765 _, offset, _, _, _ = loc.lookup(utc) 1766 } 1767 unix -= int64(offset) 1768 } 1769 1770 t := unixTime(unix, int32(nsec)) 1771 t.setLoc(loc) 1772 return t 1773 } 1774 1775 // Truncate returns the result of rounding t down to a multiple of d (since the zero time). 1776 // If d <= 0, Truncate returns t stripped of any monotonic clock reading but otherwise unchanged. 1777 // 1778 // Truncate operates on the time as an absolute duration since the 1779 // zero time; it does not operate on the presentation form of the 1780 // time. Thus, Truncate(Hour) may return a time with a non-zero 1781 // minute, depending on the time's Location. 1782 func (t Time) Truncate(d Duration) Time { 1783 t.stripMono() 1784 if d <= 0 { 1785 return t 1786 } 1787 _, r := div(t, d) 1788 return t.Add(-r) 1789 } 1790 1791 // Round returns the result of rounding t to the nearest multiple of d (since the zero time). 1792 // The rounding behavior for halfway values is to round up. 1793 // If d <= 0, Round returns t stripped of any monotonic clock reading but otherwise unchanged. 1794 // 1795 // Round operates on the time as an absolute duration since the 1796 // zero time; it does not operate on the presentation form of the 1797 // time. Thus, Round(Hour) may return a time with a non-zero 1798 // minute, depending on the time's Location. 1799 func (t Time) Round(d Duration) Time { 1800 t.stripMono() 1801 if d <= 0 { 1802 return t 1803 } 1804 _, r := div(t, d) 1805 if lessThanHalf(r, d) { 1806 return t.Add(-r) 1807 } 1808 return t.Add(d - r) 1809 } 1810 1811 // div divides t by d and returns the quotient parity and remainder. 1812 // We don't use the quotient parity anymore (round half up instead of round to even) 1813 // but it's still here in case we change our minds. 1814 func div(t Time, d Duration) (qmod2 int, r Duration) { 1815 neg := false 1816 nsec := t.nsec() 1817 sec := t.sec() 1818 if sec < 0 { 1819 // Operate on absolute value. 1820 neg = true 1821 sec = -sec 1822 nsec = -nsec 1823 if nsec < 0 { 1824 nsec += 1e9 1825 sec-- // sec >= 1 before the -- so safe 1826 } 1827 } 1828 1829 switch { 1830 // Special case: 2d divides 1 second. 1831 case d < Second && Second%(d+d) == 0: 1832 qmod2 = int(nsec/int32(d)) & 1 1833 r = Duration(nsec % int32(d)) 1834 1835 // Special case: d is a multiple of 1 second. 1836 case d%Second == 0: 1837 d1 := int64(d / Second) 1838 qmod2 = int(sec/d1) & 1 1839 r = Duration(sec%d1)*Second + Duration(nsec) 1840 1841 // General case. 1842 // This could be faster if more cleverness were applied, 1843 // but it's really only here to avoid special case restrictions in the API. 1844 // No one will care about these cases. 1845 default: 1846 // Compute nanoseconds as 128-bit number. 1847 sec := uint64(sec) 1848 tmp := (sec >> 32) * 1e9 1849 u1 := tmp >> 32 1850 u0 := tmp << 32 1851 tmp = (sec & 0xFFFFFFFF) * 1e9 1852 u0x, u0 := u0, u0+tmp 1853 if u0 < u0x { 1854 u1++ 1855 } 1856 u0x, u0 = u0, u0+uint64(nsec) 1857 if u0 < u0x { 1858 u1++ 1859 } 1860 1861 // Compute remainder by subtracting r<<k for decreasing k. 1862 // Quotient parity is whether we subtract on last round. 1863 d1 := uint64(d) 1864 for d1>>63 != 1 { 1865 d1 <<= 1 1866 } 1867 d0 := uint64(0) 1868 for { 1869 qmod2 = 0 1870 if u1 > d1 || u1 == d1 && u0 >= d0 { 1871 // subtract 1872 qmod2 = 1 1873 u0x, u0 = u0, u0-d0 1874 if u0 > u0x { 1875 u1-- 1876 } 1877 u1 -= d1 1878 } 1879 if d1 == 0 && d0 == uint64(d) { 1880 break 1881 } 1882 d0 >>= 1 1883 d0 |= (d1 & 1) << 63 1884 d1 >>= 1 1885 } 1886 r = Duration(u0) 1887 } 1888 1889 if neg && r != 0 { 1890 // If input was negative and not an exact multiple of d, we computed q, r such that 1891 // q*d + r = -t 1892 // But the right answers are given by -(q-1), d-r: 1893 // q*d + r = -t 1894 // -q*d - r = t 1895 // -(q-1)*d + (d - r) = t 1896 qmod2 ^= 1 1897 r = d - r 1898 } 1899 return 1900 } 1901 1902 // Regrettable Linkname Compatibility 1903 // 1904 // timeAbs, absDate, and absClock mimic old internal details, no longer used. 1905 // Widely used packages linknamed these to get “faster” time routines. 1906 // Notable members of the hall of shame include: 1907 // - gitee.com/quant1x/gox 1908 // - github.com/phuslu/log 1909 // 1910 // phuslu hard-coded 'Unix time + 9223372028715321600' [sic] 1911 // as the input to absDate and absClock, using the old Jan 1-based 1912 // absolute times. 1913 // quant1x linknamed the time.Time.abs method and passed the 1914 // result of that method to absDate and absClock. 1915 // 1916 // Keeping both of these working forces us to provide these three 1917 // routines here, operating on the old Jan 1-based epoch instead 1918 // of the new March 1-based epoch. And the fact that time.Time.abs 1919 // was linknamed means that we have to call the current abs method 1920 // something different (time.Time.absSec, defined above) to make it 1921 // possible to provide this simulation of the old routines here. 1922 // 1923 // None of this code is linked into the binary if not referenced by 1924 // these linkname-happy packages. In particular, despite its name, 1925 // time.Time.abs does not appear in the time.Time method table. 1926 // 1927 // Do not remove these routines or their linknames, or change the 1928 // type signature or meaning of arguments. 1929 1930 //go:linkname legacyTimeTimeAbs time.Time.abs 1931 func legacyTimeTimeAbs(t Time) uint64 { 1932 return uint64(t.absSec() - marchThruDecember*secondsPerDay) 1933 } 1934 1935 //go:linkname legacyAbsClock time.absClock 1936 func legacyAbsClock(abs uint64) (hour, min, sec int) { 1937 return absSeconds(abs + marchThruDecember*secondsPerDay).clock() 1938 } 1939 1940 //go:linkname legacyAbsDate time.absDate 1941 func legacyAbsDate(abs uint64, full bool) (year int, month Month, day int, yday int) { 1942 d := absSeconds(abs + marchThruDecember*secondsPerDay).days() 1943 year, month, day = d.date() 1944 _, yday = d.yearYday() 1945 yday-- // yearYday is 1-based, old API was 0-based 1946 return 1947 } 1948