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. 57 // 58 // Because the monotonic clock reading has no meaning outside 59 // the current process, the serialized forms generated by t.GobEncode, 60 // t.MarshalBinary, t.MarshalJSON, and t.MarshalText omit the monotonic 61 // clock reading, and t.Format provides no format for it. Similarly, the 62 // constructors time.Date, time.Parse, time.ParseInLocation, and time.Unix, 63 // as well as the unmarshalers t.GobDecode, t.UnmarshalBinary. 64 // t.UnmarshalJSON, and t.UnmarshalText always create times with 65 // no monotonic clock reading. 66 // 67 // The monotonic clock reading exists only in Time values. It is not 68 // a part of Duration values or the Unix times returned by t.Unix and 69 // friends. 70 // 71 // Note that the Go == operator compares not just the time instant but 72 // also the Location and the monotonic clock reading. See the 73 // documentation for the Time type for a discussion of equality 74 // testing for Time values. 75 // 76 // For debugging, the result of t.String does include the monotonic 77 // clock reading if present. If t != u because of different monotonic clock readings, 78 // that difference will be visible when printing t.String() and u.String(). 79 package time 80 81 import ( 82 "errors" 83 _ "unsafe" // for go:linkname 84 ) 85 86 // A Time represents an instant in time with nanosecond precision. 87 // 88 // Programs using times should typically store and pass them as values, 89 // not pointers. That is, time variables and struct fields should be of 90 // type time.Time, not *time.Time. 91 // 92 // A Time value can be used by multiple goroutines simultaneously except 93 // that the methods GobDecode, UnmarshalBinary, UnmarshalJSON and 94 // UnmarshalText are not concurrency-safe. 95 // 96 // Time instants can be compared using the Before, After, and Equal methods. 97 // The Sub method subtracts two instants, producing a Duration. 98 // The Add method adds a Time and a Duration, producing a Time. 99 // 100 // The zero value of type Time is January 1, year 1, 00:00:00.000000000 UTC. 101 // As this time is unlikely to come up in practice, the IsZero method gives 102 // a simple way of detecting a time that has not been initialized explicitly. 103 // 104 // Each Time has associated with it a Location, consulted when computing the 105 // presentation form of the time, such as in the Format, Hour, and Year methods. 106 // The methods Local, UTC, and In return a Time with a specific location. 107 // Changing the location in this way changes only the presentation; it does not 108 // change the instant in time being denoted and therefore does not affect the 109 // computations described in earlier paragraphs. 110 // 111 // Representations of a Time value saved by the GobEncode, MarshalBinary, 112 // MarshalJSON, and MarshalText methods store the Time.Location's offset, but not 113 // the location name. They therefore lose information about Daylight Saving Time. 114 // 115 // In addition to the required “wall clock” reading, a Time may contain an optional 116 // reading of the current process's monotonic clock, to provide additional precision 117 // for comparison or subtraction. 118 // See the “Monotonic Clocks” section in the package documentation for details. 119 // 120 // Note that the Go == operator compares not just the time instant but also the 121 // Location and the monotonic clock reading. Therefore, Time values should not 122 // be used as map or database keys without first guaranteeing that the 123 // identical Location has been set for all values, which can be achieved 124 // through use of the UTC or Local method, and that the monotonic clock reading 125 // has been stripped by setting t = t.Round(0). In general, prefer t.Equal(u) 126 // to t == u, since t.Equal uses the most accurate comparison available and 127 // correctly handles the case when only one of its arguments has a monotonic 128 // clock reading. 129 type Time struct { 130 // wall and ext encode the wall time seconds, wall time nanoseconds, 131 // and optional monotonic clock reading in nanoseconds. 132 // 133 // From high to low bit position, wall encodes a 1-bit flag (hasMonotonic), 134 // a 33-bit seconds field, and a 30-bit wall time nanoseconds field. 135 // The nanoseconds field is in the range [0, 999999999]. 136 // If the hasMonotonic bit is 0, then the 33-bit field must be zero 137 // and the full signed 64-bit wall seconds since Jan 1 year 1 is stored in ext. 138 // If the hasMonotonic bit is 1, then the 33-bit field holds a 33-bit 139 // unsigned wall seconds since Jan 1 year 1885, and ext holds a 140 // signed 64-bit monotonic clock reading, nanoseconds since process start. 141 wall uint64 142 ext int64 143 144 // loc specifies the Location that should be used to 145 // determine the minute, hour, month, day, and year 146 // that correspond to this Time. 147 // The nil location means UTC. 148 // All UTC times are represented with loc==nil, never loc==&utcLoc. 149 loc *Location 150 } 151 152 const ( 153 hasMonotonic = 1 << 63 154 maxWall = wallToInternal + (1<<33 - 1) // year 2157 155 minWall = wallToInternal // year 1885 156 nsecMask = 1<<30 - 1 157 nsecShift = 30 158 ) 159 160 // These helpers for manipulating the wall and monotonic clock readings 161 // take pointer receivers, even when they don't modify the time, 162 // to make them cheaper to call. 163 164 // nsec returns the time's nanoseconds. 165 func (t *Time) nsec() int32 { 166 return int32(t.wall & nsecMask) 167 } 168 169 // sec returns the time's seconds since Jan 1 year 1. 170 func (t *Time) sec() int64 { 171 if t.wall&hasMonotonic != 0 { 172 return wallToInternal + int64(t.wall<<1>>(nsecShift+1)) 173 } 174 return t.ext 175 } 176 177 // unixSec returns the time's seconds since Jan 1 1970 (Unix time). 178 func (t *Time) unixSec() int64 { return t.sec() + internalToUnix } 179 180 // addSec adds d seconds to the time. 181 func (t *Time) addSec(d int64) { 182 if t.wall&hasMonotonic != 0 { 183 sec := int64(t.wall << 1 >> (nsecShift + 1)) 184 dsec := sec + d 185 if 0 <= dsec && dsec <= 1<<33-1 { 186 t.wall = t.wall&nsecMask | uint64(dsec)<<nsecShift | hasMonotonic 187 return 188 } 189 // Wall second now out of range for packed field. 190 // Move to ext. 191 t.stripMono() 192 } 193 194 // Check if the sum of t.ext and d overflows and handle it properly. 195 sum := t.ext + d 196 if (sum > t.ext) == (d > 0) { 197 t.ext = sum 198 } else if d > 0 { 199 t.ext = 1<<63 - 1 200 } else { 201 t.ext = -(1<<63 - 1) 202 } 203 } 204 205 // setLoc sets the location associated with the time. 206 func (t *Time) setLoc(loc *Location) { 207 if loc == &utcLoc { 208 loc = nil 209 } 210 t.stripMono() 211 t.loc = loc 212 } 213 214 // stripMono strips the monotonic clock reading in t. 215 func (t *Time) stripMono() { 216 if t.wall&hasMonotonic != 0 { 217 t.ext = t.sec() 218 t.wall &= nsecMask 219 } 220 } 221 222 // setMono sets the monotonic clock reading in t. 223 // If t cannot hold a monotonic clock reading, 224 // because its wall time is too large, 225 // setMono is a no-op. 226 func (t *Time) setMono(m int64) { 227 if t.wall&hasMonotonic == 0 { 228 sec := t.ext 229 if sec < minWall || maxWall < sec { 230 return 231 } 232 t.wall |= hasMonotonic | uint64(sec-minWall)<<nsecShift 233 } 234 t.ext = m 235 } 236 237 // mono returns t's monotonic clock reading. 238 // It returns 0 for a missing reading. 239 // This function is used only for testing, 240 // so it's OK that technically 0 is a valid 241 // monotonic clock reading as well. 242 func (t *Time) mono() int64 { 243 if t.wall&hasMonotonic == 0 { 244 return 0 245 } 246 return t.ext 247 } 248 249 // After reports whether the time instant t is after u. 250 func (t Time) After(u Time) bool { 251 if t.wall&u.wall&hasMonotonic != 0 { 252 return t.ext > u.ext 253 } 254 ts := t.sec() 255 us := u.sec() 256 return ts > us || ts == us && t.nsec() > u.nsec() 257 } 258 259 // Before reports whether the time instant t is before u. 260 func (t Time) Before(u Time) bool { 261 if t.wall&u.wall&hasMonotonic != 0 { 262 return t.ext < u.ext 263 } 264 ts := t.sec() 265 us := u.sec() 266 return ts < us || ts == us && t.nsec() < u.nsec() 267 } 268 269 // Compare compares the time instant t with u. If t is before u, it returns -1; 270 // if t is after u, it returns +1; if they're the same, it returns 0. 271 func (t Time) Compare(u Time) int { 272 var tc, uc int64 273 if t.wall&u.wall&hasMonotonic != 0 { 274 tc, uc = t.ext, u.ext 275 } else { 276 tc, uc = t.sec(), u.sec() 277 if tc == uc { 278 tc, uc = int64(t.nsec()), int64(u.nsec()) 279 } 280 } 281 switch { 282 case tc < uc: 283 return -1 284 case tc > uc: 285 return +1 286 } 287 return 0 288 } 289 290 // Equal reports whether t and u represent the same time instant. 291 // Two times can be equal even if they are in different locations. 292 // For example, 6:00 +0200 and 4:00 UTC are Equal. 293 // See the documentation on the Time type for the pitfalls of using == with 294 // Time values; most code should use Equal instead. 295 func (t Time) Equal(u Time) bool { 296 if t.wall&u.wall&hasMonotonic != 0 { 297 return t.ext == u.ext 298 } 299 return t.sec() == u.sec() && t.nsec() == u.nsec() 300 } 301 302 // A Month specifies a month of the year (January = 1, ...). 303 type Month int 304 305 const ( 306 January Month = 1 + iota 307 February 308 March 309 April 310 May 311 June 312 July 313 August 314 September 315 October 316 November 317 December 318 ) 319 320 // String returns the English name of the month ("January", "February", ...). 321 func (m Month) String() string { 322 if January <= m && m <= December { 323 return longMonthNames[m-1] 324 } 325 buf := make([]byte, 20) 326 n := fmtInt(buf, uint64(m)) 327 return "%!Month(" + string(buf[n:]) + ")" 328 } 329 330 // A Weekday specifies a day of the week (Sunday = 0, ...). 331 type Weekday int 332 333 const ( 334 Sunday Weekday = iota 335 Monday 336 Tuesday 337 Wednesday 338 Thursday 339 Friday 340 Saturday 341 ) 342 343 // String returns the English name of the day ("Sunday", "Monday", ...). 344 func (d Weekday) String() string { 345 if Sunday <= d && d <= Saturday { 346 return longDayNames[d] 347 } 348 buf := make([]byte, 20) 349 n := fmtInt(buf, uint64(d)) 350 return "%!Weekday(" + string(buf[n:]) + ")" 351 } 352 353 // Computations on time. 354 // 355 // The zero value for a Time is defined to be 356 // January 1, year 1, 00:00:00.000000000 UTC 357 // which (1) looks like a zero, or as close as you can get in a date 358 // (1-1-1 00:00:00 UTC), (2) is unlikely enough to arise in practice to 359 // be a suitable "not set" sentinel, unlike Jan 1 1970, and (3) has a 360 // non-negative year even in time zones west of UTC, unlike 1-1-0 361 // 00:00:00 UTC, which would be 12-31-(-1) 19:00:00 in New York. 362 // 363 // The zero Time value does not force a specific epoch for the time 364 // representation. For example, to use the Unix epoch internally, we 365 // could define that to distinguish a zero value from Jan 1 1970, that 366 // time would be represented by sec=-1, nsec=1e9. However, it does 367 // suggest a representation, namely using 1-1-1 00:00:00 UTC as the 368 // epoch, and that's what we do. 369 // 370 // The Add and Sub computations are oblivious to the choice of epoch. 371 // 372 // The presentation computations - year, month, minute, and so on - all 373 // rely heavily on division and modulus by positive constants. For 374 // calendrical calculations we want these divisions to round down, even 375 // for negative values, so that the remainder is always positive, but 376 // Go's division (like most hardware division instructions) rounds to 377 // zero. We can still do those computations and then adjust the result 378 // for a negative numerator, but it's annoying to write the adjustment 379 // over and over. Instead, we can change to a different epoch so long 380 // ago that all the times we care about will be positive, and then round 381 // to zero and round down coincide. These presentation routines already 382 // have to add the zone offset, so adding the translation to the 383 // alternate epoch is cheap. For example, having a non-negative time t 384 // means that we can write 385 // 386 // sec = t % 60 387 // 388 // instead of 389 // 390 // sec = t % 60 391 // if sec < 0 { 392 // sec += 60 393 // } 394 // 395 // everywhere. 396 // 397 // The calendar runs on an exact 400 year cycle: a 400-year calendar 398 // printed for 1970-2369 will apply as well to 2370-2769. Even the days 399 // of the week match up. It simplifies the computations to choose the 400 // cycle boundaries so that the exceptional years are always delayed as 401 // long as possible. That means choosing a year equal to 1 mod 400, so 402 // that the first leap year is the 4th year, the first missed leap year 403 // is the 100th year, and the missed missed leap year is the 400th year. 404 // So we'd prefer instead to print a calendar for 2001-2400 and reuse it 405 // for 2401-2800. 406 // 407 // Finally, it's convenient if the delta between the Unix epoch and 408 // long-ago epoch is representable by an int64 constant. 409 // 410 // These three considerations—choose an epoch as early as possible, that 411 // uses a year equal to 1 mod 400, and that is no more than 2⁶³ seconds 412 // earlier than 1970—bring us to the year -292277022399. We refer to 413 // this year as the absolute zero year, and to times measured as a uint64 414 // seconds since this year as absolute times. 415 // 416 // Times measured as an int64 seconds since the year 1—the representation 417 // used for Time's sec field—are called internal times. 418 // 419 // Times measured as an int64 seconds since the year 1970 are called Unix 420 // times. 421 // 422 // It is tempting to just use the year 1 as the absolute epoch, defining 423 // that the routines are only valid for years >= 1. However, the 424 // routines would then be invalid when displaying the epoch in time zones 425 // west of UTC, since it is year 0. It doesn't seem tenable to say that 426 // printing the zero time correctly isn't supported in half the time 427 // zones. By comparison, it's reasonable to mishandle some times in 428 // the year -292277022399. 429 // 430 // All this is opaque to clients of the API and can be changed if a 431 // better implementation presents itself. 432 433 const ( 434 // The unsigned zero year for internal calculations. 435 // Must be 1 mod 400, and times before it will not compute correctly, 436 // but otherwise can be changed at will. 437 absoluteZeroYear = -292277022399 438 439 // The year of the zero Time. 440 // Assumed by the unixToInternal computation below. 441 internalYear = 1 442 443 // Offsets to convert between internal and absolute or Unix times. 444 absoluteToInternal int64 = (absoluteZeroYear - internalYear) * 365.2425 * secondsPerDay 445 internalToAbsolute = -absoluteToInternal 446 447 unixToInternal int64 = (1969*365 + 1969/4 - 1969/100 + 1969/400) * secondsPerDay 448 internalToUnix int64 = -unixToInternal 449 450 wallToInternal int64 = (1884*365 + 1884/4 - 1884/100 + 1884/400) * secondsPerDay 451 ) 452 453 // IsZero reports whether t represents the zero time instant, 454 // January 1, year 1, 00:00:00 UTC. 455 func (t Time) IsZero() bool { 456 return t.sec() == 0 && t.nsec() == 0 457 } 458 459 // abs returns the time t as an absolute time, adjusted by the zone offset. 460 // It is called when computing a presentation property like Month or Hour. 461 func (t Time) abs() uint64 { 462 l := t.loc 463 // Avoid function calls when possible. 464 if l == nil || l == &localLoc { 465 l = l.get() 466 } 467 sec := t.unixSec() 468 if l != &utcLoc { 469 if l.cacheZone != nil && l.cacheStart <= sec && sec < l.cacheEnd { 470 sec += int64(l.cacheZone.offset) 471 } else { 472 _, offset, _, _, _ := l.lookup(sec) 473 sec += int64(offset) 474 } 475 } 476 return uint64(sec + (unixToInternal + internalToAbsolute)) 477 } 478 479 // locabs is a combination of the Zone and abs methods, 480 // extracting both return values from a single zone lookup. 481 func (t Time) locabs() (name string, offset int, abs uint64) { 482 l := t.loc 483 if l == nil || l == &localLoc { 484 l = l.get() 485 } 486 // Avoid function call if we hit the local time cache. 487 sec := t.unixSec() 488 if l != &utcLoc { 489 if l.cacheZone != nil && l.cacheStart <= sec && sec < l.cacheEnd { 490 name = l.cacheZone.name 491 offset = l.cacheZone.offset 492 } else { 493 name, offset, _, _, _ = l.lookup(sec) 494 } 495 sec += int64(offset) 496 } else { 497 name = "UTC" 498 } 499 abs = uint64(sec + (unixToInternal + internalToAbsolute)) 500 return 501 } 502 503 // Date returns the year, month, and day in which t occurs. 504 func (t Time) Date() (year int, month Month, day int) { 505 year, month, day, _ = t.date(true) 506 return 507 } 508 509 // Year returns the year in which t occurs. 510 func (t Time) Year() int { 511 year, _, _, _ := t.date(false) 512 return year 513 } 514 515 // Month returns the month of the year specified by t. 516 func (t Time) Month() Month { 517 _, month, _, _ := t.date(true) 518 return month 519 } 520 521 // Day returns the day of the month specified by t. 522 func (t Time) Day() int { 523 _, _, day, _ := t.date(true) 524 return day 525 } 526 527 // Weekday returns the day of the week specified by t. 528 func (t Time) Weekday() Weekday { 529 return absWeekday(t.abs()) 530 } 531 532 // absWeekday is like Weekday but operates on an absolute time. 533 func absWeekday(abs uint64) Weekday { 534 // January 1 of the absolute year, like January 1 of 2001, was a Monday. 535 sec := (abs + uint64(Monday)*secondsPerDay) % secondsPerWeek 536 return Weekday(int(sec) / secondsPerDay) 537 } 538 539 // ISOWeek returns the ISO 8601 year and week number in which t occurs. 540 // Week ranges from 1 to 53. Jan 01 to Jan 03 of year n might belong to 541 // week 52 or 53 of year n-1, and Dec 29 to Dec 31 might belong to week 1 542 // of year n+1. 543 func (t Time) ISOWeek() (year, week int) { 544 // According to the rule that the first calendar week of a calendar year is 545 // the week including the first Thursday of that year, and that the last one is 546 // the week immediately preceding the first calendar week of the next calendar year. 547 // See https://www.iso.org/obp/ui#iso:std:iso:8601:-1:ed-1:v1:en:term:3.1.1.23 for details. 548 549 // weeks start with Monday 550 // Monday Tuesday Wednesday Thursday Friday Saturday Sunday 551 // 1 2 3 4 5 6 7 552 // +3 +2 +1 0 -1 -2 -3 553 // the offset to Thursday 554 abs := t.abs() 555 d := Thursday - absWeekday(abs) 556 // handle Sunday 557 if d == 4 { 558 d = -3 559 } 560 // find the Thursday of the calendar week 561 abs += uint64(d) * secondsPerDay 562 year, _, _, yday := absDate(abs, false) 563 return year, yday/7 + 1 564 } 565 566 // Clock returns the hour, minute, and second within the day specified by t. 567 func (t Time) Clock() (hour, min, sec int) { 568 return absClock(t.abs()) 569 } 570 571 // absClock is like clock but operates on an absolute time. 572 func absClock(abs uint64) (hour, min, sec int) { 573 sec = int(abs % secondsPerDay) 574 hour = sec / secondsPerHour 575 sec -= hour * secondsPerHour 576 min = sec / secondsPerMinute 577 sec -= min * secondsPerMinute 578 return 579 } 580 581 // Hour returns the hour within the day specified by t, in the range [0, 23]. 582 func (t Time) Hour() int { 583 return int(t.abs()%secondsPerDay) / secondsPerHour 584 } 585 586 // Minute returns the minute offset within the hour specified by t, in the range [0, 59]. 587 func (t Time) Minute() int { 588 return int(t.abs()%secondsPerHour) / secondsPerMinute 589 } 590 591 // Second returns the second offset within the minute specified by t, in the range [0, 59]. 592 func (t Time) Second() int { 593 return int(t.abs() % secondsPerMinute) 594 } 595 596 // Nanosecond returns the nanosecond offset within the second specified by t, 597 // in the range [0, 999999999]. 598 func (t Time) Nanosecond() int { 599 return int(t.nsec()) 600 } 601 602 // YearDay returns the day of the year specified by t, in the range [1,365] for non-leap years, 603 // and [1,366] in leap years. 604 func (t Time) YearDay() int { 605 _, _, _, yday := t.date(false) 606 return yday + 1 607 } 608 609 // A Duration represents the elapsed time between two instants 610 // as an int64 nanosecond count. The representation limits the 611 // largest representable duration to approximately 290 years. 612 type Duration int64 613 614 const ( 615 minDuration Duration = -1 << 63 616 maxDuration Duration = 1<<63 - 1 617 ) 618 619 // Common durations. There is no definition for units of Day or larger 620 // to avoid confusion across daylight savings time zone transitions. 621 // 622 // To count the number of units in a Duration, divide: 623 // 624 // second := time.Second 625 // fmt.Print(int64(second/time.Millisecond)) // prints 1000 626 // 627 // To convert an integer number of units to a Duration, multiply: 628 // 629 // seconds := 10 630 // fmt.Print(time.Duration(seconds)*time.Second) // prints 10s 631 const ( 632 Nanosecond Duration = 1 633 Microsecond = 1000 * Nanosecond 634 Millisecond = 1000 * Microsecond 635 Second = 1000 * Millisecond 636 Minute = 60 * Second 637 Hour = 60 * Minute 638 ) 639 640 // String returns a string representing the duration in the form "72h3m0.5s". 641 // Leading zero units are omitted. As a special case, durations less than one 642 // second format use a smaller unit (milli-, micro-, or nanoseconds) to ensure 643 // that the leading digit is non-zero. The zero duration formats as 0s. 644 func (d Duration) String() string { 645 // Largest time is 2540400h10m10.000000000s 646 var buf [32]byte 647 w := len(buf) 648 649 u := uint64(d) 650 neg := d < 0 651 if neg { 652 u = -u 653 } 654 655 if u < uint64(Second) { 656 // Special case: if duration is smaller than a second, 657 // use smaller units, like 1.2ms 658 var prec int 659 w-- 660 buf[w] = 's' 661 w-- 662 switch { 663 case u == 0: 664 return "0s" 665 case u < uint64(Microsecond): 666 // print nanoseconds 667 prec = 0 668 buf[w] = 'n' 669 case u < uint64(Millisecond): 670 // print microseconds 671 prec = 3 672 // U+00B5 'µ' micro sign == 0xC2 0xB5 673 w-- // Need room for two bytes. 674 copy(buf[w:], "µ") 675 default: 676 // print milliseconds 677 prec = 6 678 buf[w] = 'm' 679 } 680 w, u = fmtFrac(buf[:w], u, prec) 681 w = fmtInt(buf[:w], u) 682 } else { 683 w-- 684 buf[w] = 's' 685 686 w, u = fmtFrac(buf[:w], u, 9) 687 688 // u is now integer seconds 689 w = fmtInt(buf[:w], u%60) 690 u /= 60 691 692 // u is now integer minutes 693 if u > 0 { 694 w-- 695 buf[w] = 'm' 696 w = fmtInt(buf[:w], u%60) 697 u /= 60 698 699 // u is now integer hours 700 // Stop at hours because days can be different lengths. 701 if u > 0 { 702 w-- 703 buf[w] = 'h' 704 w = fmtInt(buf[:w], u) 705 } 706 } 707 } 708 709 if neg { 710 w-- 711 buf[w] = '-' 712 } 713 714 return string(buf[w:]) 715 } 716 717 // fmtFrac formats the fraction of v/10**prec (e.g., ".12345") into the 718 // tail of buf, omitting trailing zeros. It omits the decimal 719 // point too when the fraction is 0. It returns the index where the 720 // output bytes begin and the value v/10**prec. 721 func fmtFrac(buf []byte, v uint64, prec int) (nw int, nv uint64) { 722 // Omit trailing zeros up to and including decimal point. 723 w := len(buf) 724 print := false 725 for i := 0; i < prec; i++ { 726 digit := v % 10 727 print = print || digit != 0 728 if print { 729 w-- 730 buf[w] = byte(digit) + '0' 731 } 732 v /= 10 733 } 734 if print { 735 w-- 736 buf[w] = '.' 737 } 738 return w, v 739 } 740 741 // fmtInt formats v into the tail of buf. 742 // It returns the index where the output begins. 743 func fmtInt(buf []byte, v uint64) int { 744 w := len(buf) 745 if v == 0 { 746 w-- 747 buf[w] = '0' 748 } else { 749 for v > 0 { 750 w-- 751 buf[w] = byte(v%10) + '0' 752 v /= 10 753 } 754 } 755 return w 756 } 757 758 // Nanoseconds returns the duration as an integer nanosecond count. 759 func (d Duration) Nanoseconds() int64 { return int64(d) } 760 761 // Microseconds returns the duration as an integer microsecond count. 762 func (d Duration) Microseconds() int64 { return int64(d) / 1e3 } 763 764 // Milliseconds returns the duration as an integer millisecond count. 765 func (d Duration) Milliseconds() int64 { return int64(d) / 1e6 } 766 767 // These methods return float64 because the dominant 768 // use case is for printing a floating point number like 1.5s, and 769 // a truncation to integer would make them not useful in those cases. 770 // Splitting the integer and fraction ourselves guarantees that 771 // converting the returned float64 to an integer rounds the same 772 // way that a pure integer conversion would have, even in cases 773 // where, say, float64(d.Nanoseconds())/1e9 would have rounded 774 // differently. 775 776 // Seconds returns the duration as a floating point number of seconds. 777 func (d Duration) Seconds() float64 { 778 sec := d / Second 779 nsec := d % Second 780 return float64(sec) + float64(nsec)/1e9 781 } 782 783 // Minutes returns the duration as a floating point number of minutes. 784 func (d Duration) Minutes() float64 { 785 min := d / Minute 786 nsec := d % Minute 787 return float64(min) + float64(nsec)/(60*1e9) 788 } 789 790 // Hours returns the duration as a floating point number of hours. 791 func (d Duration) Hours() float64 { 792 hour := d / Hour 793 nsec := d % Hour 794 return float64(hour) + float64(nsec)/(60*60*1e9) 795 } 796 797 // Truncate returns the result of rounding d toward zero to a multiple of m. 798 // If m <= 0, Truncate returns d unchanged. 799 func (d Duration) Truncate(m Duration) Duration { 800 if m <= 0 { 801 return d 802 } 803 return d - d%m 804 } 805 806 // lessThanHalf reports whether x+x < y but avoids overflow, 807 // assuming x and y are both positive (Duration is signed). 808 func lessThanHalf(x, y Duration) bool { 809 return uint64(x)+uint64(x) < uint64(y) 810 } 811 812 // Round returns the result of rounding d to the nearest multiple of m. 813 // The rounding behavior for halfway values is to round away from zero. 814 // If the result exceeds the maximum (or minimum) 815 // value that can be stored in a Duration, 816 // Round returns the maximum (or minimum) duration. 817 // If m <= 0, Round returns d unchanged. 818 func (d Duration) Round(m Duration) Duration { 819 if m <= 0 { 820 return d 821 } 822 r := d % m 823 if d < 0 { 824 r = -r 825 if lessThanHalf(r, m) { 826 return d + r 827 } 828 if d1 := d - m + r; d1 < d { 829 return d1 830 } 831 return minDuration // overflow 832 } 833 if lessThanHalf(r, m) { 834 return d - r 835 } 836 if d1 := d + m - r; d1 > d { 837 return d1 838 } 839 return maxDuration // overflow 840 } 841 842 // Abs returns the absolute value of d. 843 // As a special case, math.MinInt64 is converted to math.MaxInt64. 844 func (d Duration) Abs() Duration { 845 switch { 846 case d >= 0: 847 return d 848 case d == minDuration: 849 return maxDuration 850 default: 851 return -d 852 } 853 } 854 855 // Add returns the time t+d. 856 func (t Time) Add(d Duration) Time { 857 dsec := int64(d / 1e9) 858 nsec := t.nsec() + int32(d%1e9) 859 if nsec >= 1e9 { 860 dsec++ 861 nsec -= 1e9 862 } else if nsec < 0 { 863 dsec-- 864 nsec += 1e9 865 } 866 t.wall = t.wall&^nsecMask | uint64(nsec) // update nsec 867 t.addSec(dsec) 868 if t.wall&hasMonotonic != 0 { 869 te := t.ext + int64(d) 870 if d < 0 && te > t.ext || d > 0 && te < t.ext { 871 // Monotonic clock reading now out of range; degrade to wall-only. 872 t.stripMono() 873 } else { 874 t.ext = te 875 } 876 } 877 return t 878 } 879 880 // Sub returns the duration t-u. If the result exceeds the maximum (or minimum) 881 // value that can be stored in a Duration, the maximum (or minimum) duration 882 // will be returned. 883 // To compute t-d for a duration d, use t.Add(-d). 884 func (t Time) Sub(u Time) Duration { 885 if t.wall&u.wall&hasMonotonic != 0 { 886 te := t.ext 887 ue := u.ext 888 d := Duration(te - ue) 889 if d < 0 && te > ue { 890 return maxDuration // t - u is positive out of range 891 } 892 if d > 0 && te < ue { 893 return minDuration // t - u is negative out of range 894 } 895 return d 896 } 897 d := Duration(t.sec()-u.sec())*Second + Duration(t.nsec()-u.nsec()) 898 // Check for overflow or underflow. 899 switch { 900 case u.Add(d).Equal(t): 901 return d // d is correct 902 case t.Before(u): 903 return minDuration // t - u is negative out of range 904 default: 905 return maxDuration // t - u is positive out of range 906 } 907 } 908 909 // Since returns the time elapsed since t. 910 // It is shorthand for time.Now().Sub(t). 911 func Since(t Time) Duration { 912 var now Time 913 if t.wall&hasMonotonic != 0 { 914 // Common case optimization: if t has monotonic time, then Sub will use only it. 915 now = Time{hasMonotonic, runtimeNano() - startNano, nil} 916 } else { 917 now = Now() 918 } 919 return now.Sub(t) 920 } 921 922 // Until returns the duration until t. 923 // It is shorthand for t.Sub(time.Now()). 924 func Until(t Time) Duration { 925 var now Time 926 if t.wall&hasMonotonic != 0 { 927 // Common case optimization: if t has monotonic time, then Sub will use only it. 928 now = Time{hasMonotonic, runtimeNano() - startNano, nil} 929 } else { 930 now = Now() 931 } 932 return t.Sub(now) 933 } 934 935 // AddDate returns the time corresponding to adding the 936 // given number of years, months, and days to t. 937 // For example, AddDate(-1, 2, 3) applied to January 1, 2011 938 // returns March 4, 2010. 939 // 940 // AddDate normalizes its result in the same way that Date does, 941 // so, for example, adding one month to October 31 yields 942 // December 1, the normalized form for November 31. 943 func (t Time) AddDate(years int, months int, days int) Time { 944 year, month, day := t.Date() 945 hour, min, sec := t.Clock() 946 return Date(year+years, month+Month(months), day+days, hour, min, sec, int(t.nsec()), t.Location()) 947 } 948 949 const ( 950 secondsPerMinute = 60 951 secondsPerHour = 60 * secondsPerMinute 952 secondsPerDay = 24 * secondsPerHour 953 secondsPerWeek = 7 * secondsPerDay 954 daysPer400Years = 365*400 + 97 955 daysPer100Years = 365*100 + 24 956 daysPer4Years = 365*4 + 1 957 ) 958 959 // date computes the year, day of year, and when full=true, 960 // the month and day in which t occurs. 961 func (t Time) date(full bool) (year int, month Month, day int, yday int) { 962 return absDate(t.abs(), full) 963 } 964 965 // absDate is like date but operates on an absolute time. 966 func absDate(abs uint64, full bool) (year int, month Month, day int, yday int) { 967 // Split into time and day. 968 d := abs / secondsPerDay 969 970 // Account for 400 year cycles. 971 n := d / daysPer400Years 972 y := 400 * n 973 d -= daysPer400Years * n 974 975 // Cut off 100-year cycles. 976 // The last cycle has one extra leap year, so on the last day 977 // of that year, day / daysPer100Years will be 4 instead of 3. 978 // Cut it back down to 3 by subtracting n>>2. 979 n = d / daysPer100Years 980 n -= n >> 2 981 y += 100 * n 982 d -= daysPer100Years * n 983 984 // Cut off 4-year cycles. 985 // The last cycle has a missing leap year, which does not 986 // affect the computation. 987 n = d / daysPer4Years 988 y += 4 * n 989 d -= daysPer4Years * n 990 991 // Cut off years within a 4-year cycle. 992 // The last year is a leap year, so on the last day of that year, 993 // day / 365 will be 4 instead of 3. Cut it back down to 3 994 // by subtracting n>>2. 995 n = d / 365 996 n -= n >> 2 997 y += n 998 d -= 365 * n 999 1000 year = int(int64(y) + absoluteZeroYear) 1001 yday = int(d) 1002 1003 if !full { 1004 return 1005 } 1006 1007 day = yday 1008 if isLeap(year) { 1009 // Leap year 1010 switch { 1011 case day > 31+29-1: 1012 // After leap day; pretend it wasn't there. 1013 day-- 1014 case day == 31+29-1: 1015 // Leap day. 1016 month = February 1017 day = 29 1018 return 1019 } 1020 } 1021 1022 // Estimate month on assumption that every month has 31 days. 1023 // The estimate may be too low by at most one month, so adjust. 1024 month = Month(day / 31) 1025 end := int(daysBefore[month+1]) 1026 var begin int 1027 if day >= end { 1028 month++ 1029 begin = end 1030 } else { 1031 begin = int(daysBefore[month]) 1032 } 1033 1034 month++ // because January is 1 1035 day = day - begin + 1 1036 return 1037 } 1038 1039 // daysBefore[m] counts the number of days in a non-leap year 1040 // before month m begins. There is an entry for m=12, counting 1041 // the number of days before January of next year (365). 1042 var daysBefore = [...]int32{ 1043 0, 1044 31, 1045 31 + 28, 1046 31 + 28 + 31, 1047 31 + 28 + 31 + 30, 1048 31 + 28 + 31 + 30 + 31, 1049 31 + 28 + 31 + 30 + 31 + 30, 1050 31 + 28 + 31 + 30 + 31 + 30 + 31, 1051 31 + 28 + 31 + 30 + 31 + 30 + 31 + 31, 1052 31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 30, 1053 31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 30 + 31, 1054 31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 30 + 31 + 30, 1055 31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 30 + 31 + 30 + 31, 1056 } 1057 1058 func daysIn(m Month, year int) int { 1059 if m == February && isLeap(year) { 1060 return 29 1061 } 1062 return int(daysBefore[m] - daysBefore[m-1]) 1063 } 1064 1065 // daysSinceEpoch takes a year and returns the number of days from 1066 // the absolute epoch to the start of that year. 1067 // This is basically (year - zeroYear) * 365, but accounting for leap days. 1068 func daysSinceEpoch(year int) uint64 { 1069 y := uint64(int64(year) - absoluteZeroYear) 1070 1071 // Add in days from 400-year cycles. 1072 n := y / 400 1073 y -= 400 * n 1074 d := daysPer400Years * n 1075 1076 // Add in 100-year cycles. 1077 n = y / 100 1078 y -= 100 * n 1079 d += daysPer100Years * n 1080 1081 // Add in 4-year cycles. 1082 n = y / 4 1083 y -= 4 * n 1084 d += daysPer4Years * n 1085 1086 // Add in non-leap years. 1087 n = y 1088 d += 365 * n 1089 1090 return d 1091 } 1092 1093 // Provided by package runtime. 1094 func now() (sec int64, nsec int32, mono int64) 1095 1096 // runtimeNano returns the current value of the runtime clock in nanoseconds. 1097 // 1098 //go:linkname runtimeNano runtime.nanotime 1099 func runtimeNano() int64 1100 1101 // Monotonic times are reported as offsets from startNano. 1102 // We initialize startNano to runtimeNano() - 1 so that on systems where 1103 // monotonic time resolution is fairly low (e.g. Windows 2008 1104 // which appears to have a default resolution of 15ms), 1105 // we avoid ever reporting a monotonic time of 0. 1106 // (Callers may want to use 0 as "time not set".) 1107 var startNano int64 = runtimeNano() - 1 1108 1109 // Now returns the current local time. 1110 func Now() Time { 1111 sec, nsec, mono := now() 1112 mono -= startNano 1113 sec += unixToInternal - minWall 1114 if uint64(sec)>>33 != 0 { 1115 // Seconds field overflowed the 33 bits available when 1116 // storing a monotonic time. This will be true after 1117 // March 16, 2157. 1118 return Time{uint64(nsec), sec + minWall, Local} 1119 } 1120 return Time{hasMonotonic | uint64(sec)<<nsecShift | uint64(nsec), mono, Local} 1121 } 1122 1123 func unixTime(sec int64, nsec int32) Time { 1124 return Time{uint64(nsec), sec + unixToInternal, Local} 1125 } 1126 1127 // UTC returns t with the location set to UTC. 1128 func (t Time) UTC() Time { 1129 t.setLoc(&utcLoc) 1130 return t 1131 } 1132 1133 // Local returns t with the location set to local time. 1134 func (t Time) Local() Time { 1135 t.setLoc(Local) 1136 return t 1137 } 1138 1139 // In returns a copy of t representing the same time instant, but 1140 // with the copy's location information set to loc for display 1141 // purposes. 1142 // 1143 // In panics if loc is nil. 1144 func (t Time) In(loc *Location) Time { 1145 if loc == nil { 1146 panic("time: missing Location in call to Time.In") 1147 } 1148 t.setLoc(loc) 1149 return t 1150 } 1151 1152 // Location returns the time zone information associated with t. 1153 func (t Time) Location() *Location { 1154 l := t.loc 1155 if l == nil { 1156 l = UTC 1157 } 1158 return l 1159 } 1160 1161 // Zone computes the time zone in effect at time t, returning the abbreviated 1162 // name of the zone (such as "CET") and its offset in seconds east of UTC. 1163 func (t Time) Zone() (name string, offset int) { 1164 name, offset, _, _, _ = t.loc.lookup(t.unixSec()) 1165 return 1166 } 1167 1168 // ZoneBounds returns the bounds of the time zone in effect at time t. 1169 // The zone begins at start and the next zone begins at end. 1170 // If the zone begins at the beginning of time, start will be returned as a zero Time. 1171 // If the zone goes on forever, end will be returned as a zero Time. 1172 // The Location of the returned times will be the same as t. 1173 func (t Time) ZoneBounds() (start, end Time) { 1174 _, _, startSec, endSec, _ := t.loc.lookup(t.unixSec()) 1175 if startSec != alpha { 1176 start = unixTime(startSec, 0) 1177 start.setLoc(t.loc) 1178 } 1179 if endSec != omega { 1180 end = unixTime(endSec, 0) 1181 end.setLoc(t.loc) 1182 } 1183 return 1184 } 1185 1186 // Unix returns t as a Unix time, the number of seconds elapsed 1187 // since January 1, 1970 UTC. The result does not depend on the 1188 // location associated with t. 1189 // Unix-like operating systems often record time as a 32-bit 1190 // count of seconds, but since the method here returns a 64-bit 1191 // value it is valid for billions of years into the past or future. 1192 func (t Time) Unix() int64 { 1193 return t.unixSec() 1194 } 1195 1196 // UnixMilli returns t as a Unix time, the number of milliseconds elapsed since 1197 // January 1, 1970 UTC. The result is undefined if the Unix time in 1198 // milliseconds cannot be represented by an int64 (a date more than 292 million 1199 // years before or after 1970). The result does not depend on the 1200 // location associated with t. 1201 func (t Time) UnixMilli() int64 { 1202 return t.unixSec()*1e3 + int64(t.nsec())/1e6 1203 } 1204 1205 // UnixMicro returns t as a Unix time, the number of microseconds elapsed since 1206 // January 1, 1970 UTC. The result is undefined if the Unix time in 1207 // microseconds cannot be represented by an int64 (a date before year -290307 or 1208 // after year 294246). The result does not depend on the location associated 1209 // with t. 1210 func (t Time) UnixMicro() int64 { 1211 return t.unixSec()*1e6 + int64(t.nsec())/1e3 1212 } 1213 1214 // UnixNano returns t as a Unix time, the number of nanoseconds elapsed 1215 // since January 1, 1970 UTC. The result is undefined if the Unix time 1216 // in nanoseconds cannot be represented by an int64 (a date before the year 1217 // 1678 or after 2262). Note that this means the result of calling UnixNano 1218 // on the zero Time is undefined. The result does not depend on the 1219 // location associated with t. 1220 func (t Time) UnixNano() int64 { 1221 return (t.unixSec())*1e9 + int64(t.nsec()) 1222 } 1223 1224 const ( 1225 timeBinaryVersionV1 byte = iota + 1 // For general situation 1226 timeBinaryVersionV2 // For LMT only 1227 ) 1228 1229 // MarshalBinary implements the encoding.BinaryMarshaler interface. 1230 func (t Time) MarshalBinary() ([]byte, error) { 1231 var offsetMin int16 // minutes east of UTC. -1 is UTC. 1232 var offsetSec int8 1233 version := timeBinaryVersionV1 1234 1235 if t.Location() == UTC { 1236 offsetMin = -1 1237 } else { 1238 _, offset := t.Zone() 1239 if offset%60 != 0 { 1240 version = timeBinaryVersionV2 1241 offsetSec = int8(offset % 60) 1242 } 1243 1244 offset /= 60 1245 if offset < -32768 || offset == -1 || offset > 32767 { 1246 return nil, errors.New("Time.MarshalBinary: unexpected zone offset") 1247 } 1248 offsetMin = int16(offset) 1249 } 1250 1251 sec := t.sec() 1252 nsec := t.nsec() 1253 enc := []byte{ 1254 version, // byte 0 : version 1255 byte(sec >> 56), // bytes 1-8: seconds 1256 byte(sec >> 48), 1257 byte(sec >> 40), 1258 byte(sec >> 32), 1259 byte(sec >> 24), 1260 byte(sec >> 16), 1261 byte(sec >> 8), 1262 byte(sec), 1263 byte(nsec >> 24), // bytes 9-12: nanoseconds 1264 byte(nsec >> 16), 1265 byte(nsec >> 8), 1266 byte(nsec), 1267 byte(offsetMin >> 8), // bytes 13-14: zone offset in minutes 1268 byte(offsetMin), 1269 } 1270 if version == timeBinaryVersionV2 { 1271 enc = append(enc, byte(offsetSec)) 1272 } 1273 1274 return enc, nil 1275 } 1276 1277 // UnmarshalBinary implements the encoding.BinaryUnmarshaler interface. 1278 func (t *Time) UnmarshalBinary(data []byte) error { 1279 buf := data 1280 if len(buf) == 0 { 1281 return errors.New("Time.UnmarshalBinary: no data") 1282 } 1283 1284 version := buf[0] 1285 if version != timeBinaryVersionV1 && version != timeBinaryVersionV2 { 1286 return errors.New("Time.UnmarshalBinary: unsupported version") 1287 } 1288 1289 wantLen := /*version*/ 1 + /*sec*/ 8 + /*nsec*/ 4 + /*zone offset*/ 2 1290 if version == timeBinaryVersionV2 { 1291 wantLen++ 1292 } 1293 if len(buf) != wantLen { 1294 return errors.New("Time.UnmarshalBinary: invalid length") 1295 } 1296 1297 buf = buf[1:] 1298 sec := int64(buf[7]) | int64(buf[6])<<8 | int64(buf[5])<<16 | int64(buf[4])<<24 | 1299 int64(buf[3])<<32 | int64(buf[2])<<40 | int64(buf[1])<<48 | int64(buf[0])<<56 1300 1301 buf = buf[8:] 1302 nsec := int32(buf[3]) | int32(buf[2])<<8 | int32(buf[1])<<16 | int32(buf[0])<<24 1303 1304 buf = buf[4:] 1305 offset := int(int16(buf[1])|int16(buf[0])<<8) * 60 1306 if version == timeBinaryVersionV2 { 1307 offset += int(buf[2]) 1308 } 1309 1310 *t = Time{} 1311 t.wall = uint64(nsec) 1312 t.ext = sec 1313 1314 if offset == -1*60 { 1315 t.setLoc(&utcLoc) 1316 } else if _, localoff, _, _, _ := Local.lookup(t.unixSec()); offset == localoff { 1317 t.setLoc(Local) 1318 } else { 1319 t.setLoc(FixedZone("", offset)) 1320 } 1321 1322 return nil 1323 } 1324 1325 // TODO(rsc): Remove GobEncoder, GobDecoder, MarshalJSON, UnmarshalJSON in Go 2. 1326 // The same semantics will be provided by the generic MarshalBinary, MarshalText, 1327 // UnmarshalBinary, UnmarshalText. 1328 1329 // GobEncode implements the gob.GobEncoder interface. 1330 func (t Time) GobEncode() ([]byte, error) { 1331 return t.MarshalBinary() 1332 } 1333 1334 // GobDecode implements the gob.GobDecoder interface. 1335 func (t *Time) GobDecode(data []byte) error { 1336 return t.UnmarshalBinary(data) 1337 } 1338 1339 // MarshalJSON implements the json.Marshaler interface. 1340 // The time is a quoted string in the RFC 3339 format with sub-second precision. 1341 // If the timestamp cannot be represented as valid RFC 3339 1342 // (e.g., the year is out of range), then an error is reported. 1343 func (t Time) MarshalJSON() ([]byte, error) { 1344 b := make([]byte, 0, len(RFC3339Nano)+len(`""`)) 1345 b = append(b, '"') 1346 b, err := t.appendStrictRFC3339(b) 1347 b = append(b, '"') 1348 if err != nil { 1349 return nil, errors.New("Time.MarshalJSON: " + err.Error()) 1350 } 1351 return b, nil 1352 } 1353 1354 // UnmarshalJSON implements the json.Unmarshaler interface. 1355 // The time must be a quoted string in the RFC 3339 format. 1356 func (t *Time) UnmarshalJSON(data []byte) error { 1357 if string(data) == "null" { 1358 return nil 1359 } 1360 // TODO(https://go.dev/issue/47353): Properly unescape a JSON string. 1361 if len(data) < 2 || data[0] != '"' || data[len(data)-1] != '"' { 1362 return errors.New("Time.UnmarshalJSON: input is not a JSON string") 1363 } 1364 data = data[len(`"`) : len(data)-len(`"`)] 1365 var err error 1366 *t, err = parseStrictRFC3339(data) 1367 return err 1368 } 1369 1370 // MarshalText implements the encoding.TextMarshaler interface. 1371 // The time is formatted in RFC 3339 format with sub-second precision. 1372 // If the timestamp cannot be represented as valid RFC 3339 1373 // (e.g., the year is out of range), then an error is reported. 1374 func (t Time) MarshalText() ([]byte, error) { 1375 b := make([]byte, 0, len(RFC3339Nano)) 1376 b, err := t.appendStrictRFC3339(b) 1377 if err != nil { 1378 return nil, errors.New("Time.MarshalText: " + err.Error()) 1379 } 1380 return b, nil 1381 } 1382 1383 // UnmarshalText implements the encoding.TextUnmarshaler interface. 1384 // The time must be in the RFC 3339 format. 1385 func (t *Time) UnmarshalText(data []byte) error { 1386 var err error 1387 *t, err = parseStrictRFC3339(data) 1388 return err 1389 } 1390 1391 // Unix returns the local Time corresponding to the given Unix time, 1392 // sec seconds and nsec nanoseconds since January 1, 1970 UTC. 1393 // It is valid to pass nsec outside the range [0, 999999999]. 1394 // Not all sec values have a corresponding time value. One such 1395 // value is 1<<63-1 (the largest int64 value). 1396 func Unix(sec int64, nsec int64) Time { 1397 if nsec < 0 || nsec >= 1e9 { 1398 n := nsec / 1e9 1399 sec += n 1400 nsec -= n * 1e9 1401 if nsec < 0 { 1402 nsec += 1e9 1403 sec-- 1404 } 1405 } 1406 return unixTime(sec, int32(nsec)) 1407 } 1408 1409 // UnixMilli returns the local Time corresponding to the given Unix time, 1410 // msec milliseconds since January 1, 1970 UTC. 1411 func UnixMilli(msec int64) Time { 1412 return Unix(msec/1e3, (msec%1e3)*1e6) 1413 } 1414 1415 // UnixMicro returns the local Time corresponding to the given Unix time, 1416 // usec microseconds since January 1, 1970 UTC. 1417 func UnixMicro(usec int64) Time { 1418 return Unix(usec/1e6, (usec%1e6)*1e3) 1419 } 1420 1421 // IsDST reports whether the time in the configured location is in Daylight Savings Time. 1422 func (t Time) IsDST() bool { 1423 _, _, _, _, isDST := t.loc.lookup(t.Unix()) 1424 return isDST 1425 } 1426 1427 func isLeap(year int) bool { 1428 return year%4 == 0 && (year%100 != 0 || year%400 == 0) 1429 } 1430 1431 // norm returns nhi, nlo such that 1432 // 1433 // hi * base + lo == nhi * base + nlo 1434 // 0 <= nlo < base 1435 func norm(hi, lo, base int) (nhi, nlo int) { 1436 if lo < 0 { 1437 n := (-lo-1)/base + 1 1438 hi -= n 1439 lo += n * base 1440 } 1441 if lo >= base { 1442 n := lo / base 1443 hi += n 1444 lo -= n * base 1445 } 1446 return hi, lo 1447 } 1448 1449 // Date returns the Time corresponding to 1450 // 1451 // yyyy-mm-dd hh:mm:ss + nsec nanoseconds 1452 // 1453 // in the appropriate zone for that time in the given location. 1454 // 1455 // The month, day, hour, min, sec, and nsec values may be outside 1456 // their usual ranges and will be normalized during the conversion. 1457 // For example, October 32 converts to November 1. 1458 // 1459 // A daylight savings time transition skips or repeats times. 1460 // For example, in the United States, March 13, 2011 2:15am never occurred, 1461 // while November 6, 2011 1:15am occurred twice. In such cases, the 1462 // choice of time zone, and therefore the time, is not well-defined. 1463 // Date returns a time that is correct in one of the two zones involved 1464 // in the transition, but it does not guarantee which. 1465 // 1466 // Date panics if loc is nil. 1467 func Date(year int, month Month, day, hour, min, sec, nsec int, loc *Location) Time { 1468 if loc == nil { 1469 panic("time: missing Location in call to Date") 1470 } 1471 1472 // Normalize month, overflowing into year. 1473 m := int(month) - 1 1474 year, m = norm(year, m, 12) 1475 month = Month(m) + 1 1476 1477 // Normalize nsec, sec, min, hour, overflowing into day. 1478 sec, nsec = norm(sec, nsec, 1e9) 1479 min, sec = norm(min, sec, 60) 1480 hour, min = norm(hour, min, 60) 1481 day, hour = norm(day, hour, 24) 1482 1483 // Compute days since the absolute epoch. 1484 d := daysSinceEpoch(year) 1485 1486 // Add in days before this month. 1487 d += uint64(daysBefore[month-1]) 1488 if isLeap(year) && month >= March { 1489 d++ // February 29 1490 } 1491 1492 // Add in days before today. 1493 d += uint64(day - 1) 1494 1495 // Add in time elapsed today. 1496 abs := d * secondsPerDay 1497 abs += uint64(hour*secondsPerHour + min*secondsPerMinute + sec) 1498 1499 unix := int64(abs) + (absoluteToInternal + internalToUnix) 1500 1501 // Look for zone offset for expected time, so we can adjust to UTC. 1502 // The lookup function expects UTC, so first we pass unix in the 1503 // hope that it will not be too close to a zone transition, 1504 // and then adjust if it is. 1505 _, offset, start, end, _ := loc.lookup(unix) 1506 if offset != 0 { 1507 utc := unix - int64(offset) 1508 // If utc is valid for the time zone we found, then we have the right offset. 1509 // If not, we get the correct offset by looking up utc in the location. 1510 if utc < start || utc >= end { 1511 _, offset, _, _, _ = loc.lookup(utc) 1512 } 1513 unix -= int64(offset) 1514 } 1515 1516 t := unixTime(unix, int32(nsec)) 1517 t.setLoc(loc) 1518 return t 1519 } 1520 1521 // Truncate returns the result of rounding t down to a multiple of d (since the zero time). 1522 // If d <= 0, Truncate returns t stripped of any monotonic clock reading but otherwise unchanged. 1523 // 1524 // Truncate operates on the time as an absolute duration since the 1525 // zero time; it does not operate on the presentation form of the 1526 // time. Thus, Truncate(Hour) may return a time with a non-zero 1527 // minute, depending on the time's Location. 1528 func (t Time) Truncate(d Duration) Time { 1529 t.stripMono() 1530 if d <= 0 { 1531 return t 1532 } 1533 _, r := div(t, d) 1534 return t.Add(-r) 1535 } 1536 1537 // Round returns the result of rounding t to the nearest multiple of d (since the zero time). 1538 // The rounding behavior for halfway values is to round up. 1539 // If d <= 0, Round returns t stripped of any monotonic clock reading but otherwise unchanged. 1540 // 1541 // Round operates on the time as an absolute duration since the 1542 // zero time; it does not operate on the presentation form of the 1543 // time. Thus, Round(Hour) may return a time with a non-zero 1544 // minute, depending on the time's Location. 1545 func (t Time) Round(d Duration) Time { 1546 t.stripMono() 1547 if d <= 0 { 1548 return t 1549 } 1550 _, r := div(t, d) 1551 if lessThanHalf(r, d) { 1552 return t.Add(-r) 1553 } 1554 return t.Add(d - r) 1555 } 1556 1557 // div divides t by d and returns the quotient parity and remainder. 1558 // We don't use the quotient parity anymore (round half up instead of round to even) 1559 // but it's still here in case we change our minds. 1560 func div(t Time, d Duration) (qmod2 int, r Duration) { 1561 neg := false 1562 nsec := t.nsec() 1563 sec := t.sec() 1564 if sec < 0 { 1565 // Operate on absolute value. 1566 neg = true 1567 sec = -sec 1568 nsec = -nsec 1569 if nsec < 0 { 1570 nsec += 1e9 1571 sec-- // sec >= 1 before the -- so safe 1572 } 1573 } 1574 1575 switch { 1576 // Special case: 2d divides 1 second. 1577 case d < Second && Second%(d+d) == 0: 1578 qmod2 = int(nsec/int32(d)) & 1 1579 r = Duration(nsec % int32(d)) 1580 1581 // Special case: d is a multiple of 1 second. 1582 case d%Second == 0: 1583 d1 := int64(d / Second) 1584 qmod2 = int(sec/d1) & 1 1585 r = Duration(sec%d1)*Second + Duration(nsec) 1586 1587 // General case. 1588 // This could be faster if more cleverness were applied, 1589 // but it's really only here to avoid special case restrictions in the API. 1590 // No one will care about these cases. 1591 default: 1592 // Compute nanoseconds as 128-bit number. 1593 sec := uint64(sec) 1594 tmp := (sec >> 32) * 1e9 1595 u1 := tmp >> 32 1596 u0 := tmp << 32 1597 tmp = (sec & 0xFFFFFFFF) * 1e9 1598 u0x, u0 := u0, u0+tmp 1599 if u0 < u0x { 1600 u1++ 1601 } 1602 u0x, u0 = u0, u0+uint64(nsec) 1603 if u0 < u0x { 1604 u1++ 1605 } 1606 1607 // Compute remainder by subtracting r<<k for decreasing k. 1608 // Quotient parity is whether we subtract on last round. 1609 d1 := uint64(d) 1610 for d1>>63 != 1 { 1611 d1 <<= 1 1612 } 1613 d0 := uint64(0) 1614 for { 1615 qmod2 = 0 1616 if u1 > d1 || u1 == d1 && u0 >= d0 { 1617 // subtract 1618 qmod2 = 1 1619 u0x, u0 = u0, u0-d0 1620 if u0 > u0x { 1621 u1-- 1622 } 1623 u1 -= d1 1624 } 1625 if d1 == 0 && d0 == uint64(d) { 1626 break 1627 } 1628 d0 >>= 1 1629 d0 |= (d1 & 1) << 63 1630 d1 >>= 1 1631 } 1632 r = Duration(u0) 1633 } 1634 1635 if neg && r != 0 { 1636 // If input was negative and not an exact multiple of d, we computed q, r such that 1637 // q*d + r = -t 1638 // But the right answers are given by -(q-1), d-r: 1639 // q*d + r = -t 1640 // -q*d - r = t 1641 // -(q-1)*d + (d - r) = t 1642 qmod2 ^= 1 1643 r = d - r 1644 } 1645 return 1646 } 1647