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), 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 // Equal reports whether t and u represent the same time instant. 270 // Two times can be equal even if they are in different locations. 271 // For example, 6:00 +0200 and 4:00 UTC are Equal. 272 // See the documentation on the Time type for the pitfalls of using == with 273 // Time values; most code should use Equal instead. 274 func (t Time) Equal(u Time) bool { 275 if t.wall&u.wall&hasMonotonic != 0 { 276 return t.ext == u.ext 277 } 278 return t.sec() == u.sec() && t.nsec() == u.nsec() 279 } 280 281 // A Month specifies a month of the year (January = 1, ...). 282 type Month int 283 284 const ( 285 January Month = 1 + iota 286 February 287 March 288 April 289 May 290 June 291 July 292 August 293 September 294 October 295 November 296 December 297 ) 298 299 // String returns the English name of the month ("January", "February", ...). 300 func (m Month) String() string { 301 if January <= m && m <= December { 302 return longMonthNames[m-1] 303 } 304 buf := make([]byte, 20) 305 n := fmtInt(buf, uint64(m)) 306 return "%!Month(" + string(buf[n:]) + ")" 307 } 308 309 // A Weekday specifies a day of the week (Sunday = 0, ...). 310 type Weekday int 311 312 const ( 313 Sunday Weekday = iota 314 Monday 315 Tuesday 316 Wednesday 317 Thursday 318 Friday 319 Saturday 320 ) 321 322 // String returns the English name of the day ("Sunday", "Monday", ...). 323 func (d Weekday) String() string { 324 if Sunday <= d && d <= Saturday { 325 return longDayNames[d] 326 } 327 buf := make([]byte, 20) 328 n := fmtInt(buf, uint64(d)) 329 return "%!Weekday(" + string(buf[n:]) + ")" 330 } 331 332 // Computations on time. 333 // 334 // The zero value for a Time is defined to be 335 // January 1, year 1, 00:00:00.000000000 UTC 336 // which (1) looks like a zero, or as close as you can get in a date 337 // (1-1-1 00:00:00 UTC), (2) is unlikely enough to arise in practice to 338 // be a suitable "not set" sentinel, unlike Jan 1 1970, and (3) has a 339 // non-negative year even in time zones west of UTC, unlike 1-1-0 340 // 00:00:00 UTC, which would be 12-31-(-1) 19:00:00 in New York. 341 // 342 // The zero Time value does not force a specific epoch for the time 343 // representation. For example, to use the Unix epoch internally, we 344 // could define that to distinguish a zero value from Jan 1 1970, that 345 // time would be represented by sec=-1, nsec=1e9. However, it does 346 // suggest a representation, namely using 1-1-1 00:00:00 UTC as the 347 // epoch, and that's what we do. 348 // 349 // The Add and Sub computations are oblivious to the choice of epoch. 350 // 351 // The presentation computations - year, month, minute, and so on - all 352 // rely heavily on division and modulus by positive constants. For 353 // calendrical calculations we want these divisions to round down, even 354 // for negative values, so that the remainder is always positive, but 355 // Go's division (like most hardware division instructions) rounds to 356 // zero. We can still do those computations and then adjust the result 357 // for a negative numerator, but it's annoying to write the adjustment 358 // over and over. Instead, we can change to a different epoch so long 359 // ago that all the times we care about will be positive, and then round 360 // to zero and round down coincide. These presentation routines already 361 // have to add the zone offset, so adding the translation to the 362 // alternate epoch is cheap. For example, having a non-negative time t 363 // means that we can write 364 // 365 // sec = t % 60 366 // 367 // instead of 368 // 369 // sec = t % 60 370 // if sec < 0 { 371 // sec += 60 372 // } 373 // 374 // everywhere. 375 // 376 // The calendar runs on an exact 400 year cycle: a 400-year calendar 377 // printed for 1970-2369 will apply as well to 2370-2769. Even the days 378 // of the week match up. It simplifies the computations to choose the 379 // cycle boundaries so that the exceptional years are always delayed as 380 // long as possible. That means choosing a year equal to 1 mod 400, so 381 // that the first leap year is the 4th year, the first missed leap year 382 // is the 100th year, and the missed missed leap year is the 400th year. 383 // So we'd prefer instead to print a calendar for 2001-2400 and reuse it 384 // for 2401-2800. 385 // 386 // Finally, it's convenient if the delta between the Unix epoch and 387 // long-ago epoch is representable by an int64 constant. 388 // 389 // These three considerations—choose an epoch as early as possible, that 390 // uses a year equal to 1 mod 400, and that is no more than 2⁶³ seconds 391 // earlier than 1970—bring us to the year -292277022399. We refer to 392 // this year as the absolute zero year, and to times measured as a uint64 393 // seconds since this year as absolute times. 394 // 395 // Times measured as an int64 seconds since the year 1—the representation 396 // used for Time's sec field—are called internal times. 397 // 398 // Times measured as an int64 seconds since the year 1970 are called Unix 399 // times. 400 // 401 // It is tempting to just use the year 1 as the absolute epoch, defining 402 // that the routines are only valid for years >= 1. However, the 403 // routines would then be invalid when displaying the epoch in time zones 404 // west of UTC, since it is year 0. It doesn't seem tenable to say that 405 // printing the zero time correctly isn't supported in half the time 406 // zones. By comparison, it's reasonable to mishandle some times in 407 // the year -292277022399. 408 // 409 // All this is opaque to clients of the API and can be changed if a 410 // better implementation presents itself. 411 412 const ( 413 // The unsigned zero year for internal calculations. 414 // Must be 1 mod 400, and times before it will not compute correctly, 415 // but otherwise can be changed at will. 416 absoluteZeroYear = -292277022399 417 418 // The year of the zero Time. 419 // Assumed by the unixToInternal computation below. 420 internalYear = 1 421 422 // Offsets to convert between internal and absolute or Unix times. 423 absoluteToInternal int64 = (absoluteZeroYear - internalYear) * 365.2425 * secondsPerDay 424 internalToAbsolute = -absoluteToInternal 425 426 unixToInternal int64 = (1969*365 + 1969/4 - 1969/100 + 1969/400) * secondsPerDay 427 internalToUnix int64 = -unixToInternal 428 429 wallToInternal int64 = (1884*365 + 1884/4 - 1884/100 + 1884/400) * secondsPerDay 430 ) 431 432 // IsZero reports whether t represents the zero time instant, 433 // January 1, year 1, 00:00:00 UTC. 434 func (t Time) IsZero() bool { 435 return t.sec() == 0 && t.nsec() == 0 436 } 437 438 // abs returns the time t as an absolute time, adjusted by the zone offset. 439 // It is called when computing a presentation property like Month or Hour. 440 func (t Time) abs() uint64 { 441 l := t.loc 442 // Avoid function calls when possible. 443 if l == nil || l == &localLoc { 444 l = l.get() 445 } 446 sec := t.unixSec() 447 if l != &utcLoc { 448 if l.cacheZone != nil && l.cacheStart <= sec && sec < l.cacheEnd { 449 sec += int64(l.cacheZone.offset) 450 } else { 451 _, offset, _, _, _ := l.lookup(sec) 452 sec += int64(offset) 453 } 454 } 455 return uint64(sec + (unixToInternal + internalToAbsolute)) 456 } 457 458 // locabs is a combination of the Zone and abs methods, 459 // extracting both return values from a single zone lookup. 460 func (t Time) locabs() (name string, offset int, abs uint64) { 461 l := t.loc 462 if l == nil || l == &localLoc { 463 l = l.get() 464 } 465 // Avoid function call if we hit the local time cache. 466 sec := t.unixSec() 467 if l != &utcLoc { 468 if l.cacheZone != nil && l.cacheStart <= sec && sec < l.cacheEnd { 469 name = l.cacheZone.name 470 offset = l.cacheZone.offset 471 } else { 472 name, offset, _, _, _ = l.lookup(sec) 473 } 474 sec += int64(offset) 475 } else { 476 name = "UTC" 477 } 478 abs = uint64(sec + (unixToInternal + internalToAbsolute)) 479 return 480 } 481 482 // Date returns the year, month, and day in which t occurs. 483 func (t Time) Date() (year int, month Month, day int) { 484 year, month, day, _ = t.date(true) 485 return 486 } 487 488 // Year returns the year in which t occurs. 489 func (t Time) Year() int { 490 year, _, _, _ := t.date(false) 491 return year 492 } 493 494 // Month returns the month of the year specified by t. 495 func (t Time) Month() Month { 496 _, month, _, _ := t.date(true) 497 return month 498 } 499 500 // Day returns the day of the month specified by t. 501 func (t Time) Day() int { 502 _, _, day, _ := t.date(true) 503 return day 504 } 505 506 // Weekday returns the day of the week specified by t. 507 func (t Time) Weekday() Weekday { 508 return absWeekday(t.abs()) 509 } 510 511 // absWeekday is like Weekday but operates on an absolute time. 512 func absWeekday(abs uint64) Weekday { 513 // January 1 of the absolute year, like January 1 of 2001, was a Monday. 514 sec := (abs + uint64(Monday)*secondsPerDay) % secondsPerWeek 515 return Weekday(int(sec) / secondsPerDay) 516 } 517 518 // ISOWeek returns the ISO 8601 year and week number in which t occurs. 519 // Week ranges from 1 to 53. Jan 01 to Jan 03 of year n might belong to 520 // week 52 or 53 of year n-1, and Dec 29 to Dec 31 might belong to week 1 521 // of year n+1. 522 func (t Time) ISOWeek() (year, week int) { 523 // According to the rule that the first calendar week of a calendar year is 524 // the week including the first Thursday of that year, and that the last one is 525 // the week immediately preceding the first calendar week of the next calendar year. 526 // See https://www.iso.org/obp/ui#iso:std:iso:8601:-1:ed-1:v1:en:term:3.1.1.23 for details. 527 528 // weeks start with Monday 529 // Monday Tuesday Wednesday Thursday Friday Saturday Sunday 530 // 1 2 3 4 5 6 7 531 // +3 +2 +1 0 -1 -2 -3 532 // the offset to Thursday 533 abs := t.abs() 534 d := Thursday - absWeekday(abs) 535 // handle Sunday 536 if d == 4 { 537 d = -3 538 } 539 // find the Thursday of the calendar week 540 abs += uint64(d) * secondsPerDay 541 year, _, _, yday := absDate(abs, false) 542 return year, yday/7 + 1 543 } 544 545 // Clock returns the hour, minute, and second within the day specified by t. 546 func (t Time) Clock() (hour, min, sec int) { 547 return absClock(t.abs()) 548 } 549 550 // absClock is like clock but operates on an absolute time. 551 func absClock(abs uint64) (hour, min, sec int) { 552 sec = int(abs % secondsPerDay) 553 hour = sec / secondsPerHour 554 sec -= hour * secondsPerHour 555 min = sec / secondsPerMinute 556 sec -= min * secondsPerMinute 557 return 558 } 559 560 // Hour returns the hour within the day specified by t, in the range [0, 23]. 561 func (t Time) Hour() int { 562 return int(t.abs()%secondsPerDay) / secondsPerHour 563 } 564 565 // Minute returns the minute offset within the hour specified by t, in the range [0, 59]. 566 func (t Time) Minute() int { 567 return int(t.abs()%secondsPerHour) / secondsPerMinute 568 } 569 570 // Second returns the second offset within the minute specified by t, in the range [0, 59]. 571 func (t Time) Second() int { 572 return int(t.abs() % secondsPerMinute) 573 } 574 575 // Nanosecond returns the nanosecond offset within the second specified by t, 576 // in the range [0, 999999999]. 577 func (t Time) Nanosecond() int { 578 return int(t.nsec()) 579 } 580 581 // YearDay returns the day of the year specified by t, in the range [1,365] for non-leap years, 582 // and [1,366] in leap years. 583 func (t Time) YearDay() int { 584 _, _, _, yday := t.date(false) 585 return yday + 1 586 } 587 588 // A Duration represents the elapsed time between two instants 589 // as an int64 nanosecond count. The representation limits the 590 // largest representable duration to approximately 290 years. 591 type Duration int64 592 593 const ( 594 minDuration Duration = -1 << 63 595 maxDuration Duration = 1<<63 - 1 596 ) 597 598 // Common durations. There is no definition for units of Day or larger 599 // to avoid confusion across daylight savings time zone transitions. 600 // 601 // To count the number of units in a Duration, divide: 602 // 603 // second := time.Second 604 // fmt.Print(int64(second/time.Millisecond)) // prints 1000 605 // 606 // To convert an integer number of units to a Duration, multiply: 607 // 608 // seconds := 10 609 // fmt.Print(time.Duration(seconds)*time.Second) // prints 10s 610 const ( 611 Nanosecond Duration = 1 612 Microsecond = 1000 * Nanosecond 613 Millisecond = 1000 * Microsecond 614 Second = 1000 * Millisecond 615 Minute = 60 * Second 616 Hour = 60 * Minute 617 ) 618 619 // String returns a string representing the duration in the form "72h3m0.5s". 620 // Leading zero units are omitted. As a special case, durations less than one 621 // second format use a smaller unit (milli-, micro-, or nanoseconds) to ensure 622 // that the leading digit is non-zero. The zero duration formats as 0s. 623 func (d Duration) String() string { 624 // Largest time is 2540400h10m10.000000000s 625 var buf [32]byte 626 w := len(buf) 627 628 u := uint64(d) 629 neg := d < 0 630 if neg { 631 u = -u 632 } 633 634 if u < uint64(Second) { 635 // Special case: if duration is smaller than a second, 636 // use smaller units, like 1.2ms 637 var prec int 638 w-- 639 buf[w] = 's' 640 w-- 641 switch { 642 case u == 0: 643 return "0s" 644 case u < uint64(Microsecond): 645 // print nanoseconds 646 prec = 0 647 buf[w] = 'n' 648 case u < uint64(Millisecond): 649 // print microseconds 650 prec = 3 651 // U+00B5 'µ' micro sign == 0xC2 0xB5 652 w-- // Need room for two bytes. 653 copy(buf[w:], "µ") 654 default: 655 // print milliseconds 656 prec = 6 657 buf[w] = 'm' 658 } 659 w, u = fmtFrac(buf[:w], u, prec) 660 w = fmtInt(buf[:w], u) 661 } else { 662 w-- 663 buf[w] = 's' 664 665 w, u = fmtFrac(buf[:w], u, 9) 666 667 // u is now integer seconds 668 w = fmtInt(buf[:w], u%60) 669 u /= 60 670 671 // u is now integer minutes 672 if u > 0 { 673 w-- 674 buf[w] = 'm' 675 w = fmtInt(buf[:w], u%60) 676 u /= 60 677 678 // u is now integer hours 679 // Stop at hours because days can be different lengths. 680 if u > 0 { 681 w-- 682 buf[w] = 'h' 683 w = fmtInt(buf[:w], u) 684 } 685 } 686 } 687 688 if neg { 689 w-- 690 buf[w] = '-' 691 } 692 693 return string(buf[w:]) 694 } 695 696 // fmtFrac formats the fraction of v/10**prec (e.g., ".12345") into the 697 // tail of buf, omitting trailing zeros. It omits the decimal 698 // point too when the fraction is 0. It returns the index where the 699 // output bytes begin and the value v/10**prec. 700 func fmtFrac(buf []byte, v uint64, prec int) (nw int, nv uint64) { 701 // Omit trailing zeros up to and including decimal point. 702 w := len(buf) 703 print := false 704 for i := 0; i < prec; i++ { 705 digit := v % 10 706 print = print || digit != 0 707 if print { 708 w-- 709 buf[w] = byte(digit) + '0' 710 } 711 v /= 10 712 } 713 if print { 714 w-- 715 buf[w] = '.' 716 } 717 return w, v 718 } 719 720 // fmtInt formats v into the tail of buf. 721 // It returns the index where the output begins. 722 func fmtInt(buf []byte, v uint64) int { 723 w := len(buf) 724 if v == 0 { 725 w-- 726 buf[w] = '0' 727 } else { 728 for v > 0 { 729 w-- 730 buf[w] = byte(v%10) + '0' 731 v /= 10 732 } 733 } 734 return w 735 } 736 737 // Nanoseconds returns the duration as an integer nanosecond count. 738 func (d Duration) Nanoseconds() int64 { return int64(d) } 739 740 // Microseconds returns the duration as an integer microsecond count. 741 func (d Duration) Microseconds() int64 { return int64(d) / 1e3 } 742 743 // Milliseconds returns the duration as an integer millisecond count. 744 func (d Duration) Milliseconds() int64 { return int64(d) / 1e6 } 745 746 // These methods return float64 because the dominant 747 // use case is for printing a floating point number like 1.5s, and 748 // a truncation to integer would make them not useful in those cases. 749 // Splitting the integer and fraction ourselves guarantees that 750 // converting the returned float64 to an integer rounds the same 751 // way that a pure integer conversion would have, even in cases 752 // where, say, float64(d.Nanoseconds())/1e9 would have rounded 753 // differently. 754 755 // Seconds returns the duration as a floating point number of seconds. 756 func (d Duration) Seconds() float64 { 757 sec := d / Second 758 nsec := d % Second 759 return float64(sec) + float64(nsec)/1e9 760 } 761 762 // Minutes returns the duration as a floating point number of minutes. 763 func (d Duration) Minutes() float64 { 764 min := d / Minute 765 nsec := d % Minute 766 return float64(min) + float64(nsec)/(60*1e9) 767 } 768 769 // Hours returns the duration as a floating point number of hours. 770 func (d Duration) Hours() float64 { 771 hour := d / Hour 772 nsec := d % Hour 773 return float64(hour) + float64(nsec)/(60*60*1e9) 774 } 775 776 // Truncate returns the result of rounding d toward zero to a multiple of m. 777 // If m <= 0, Truncate returns d unchanged. 778 func (d Duration) Truncate(m Duration) Duration { 779 if m <= 0 { 780 return d 781 } 782 return d - d%m 783 } 784 785 // lessThanHalf reports whether x+x < y but avoids overflow, 786 // assuming x and y are both positive (Duration is signed). 787 func lessThanHalf(x, y Duration) bool { 788 return uint64(x)+uint64(x) < uint64(y) 789 } 790 791 // Round returns the result of rounding d to the nearest multiple of m. 792 // The rounding behavior for halfway values is to round away from zero. 793 // If the result exceeds the maximum (or minimum) 794 // value that can be stored in a Duration, 795 // Round returns the maximum (or minimum) duration. 796 // If m <= 0, Round returns d unchanged. 797 func (d Duration) Round(m Duration) Duration { 798 if m <= 0 { 799 return d 800 } 801 r := d % m 802 if d < 0 { 803 r = -r 804 if lessThanHalf(r, m) { 805 return d + r 806 } 807 if d1 := d - m + r; d1 < d { 808 return d1 809 } 810 return minDuration // overflow 811 } 812 if lessThanHalf(r, m) { 813 return d - r 814 } 815 if d1 := d + m - r; d1 > d { 816 return d1 817 } 818 return maxDuration // overflow 819 } 820 821 // Abs returns the absolute value of d. 822 // As a special case, math.MinInt64 is converted to math.MaxInt64. 823 func (d Duration) Abs() Duration { 824 switch { 825 case d >= 0: 826 return d 827 case d == minDuration: 828 return maxDuration 829 default: 830 return -d 831 } 832 } 833 834 // Add returns the time t+d. 835 func (t Time) Add(d Duration) Time { 836 dsec := int64(d / 1e9) 837 nsec := t.nsec() + int32(d%1e9) 838 if nsec >= 1e9 { 839 dsec++ 840 nsec -= 1e9 841 } else if nsec < 0 { 842 dsec-- 843 nsec += 1e9 844 } 845 t.wall = t.wall&^nsecMask | uint64(nsec) // update nsec 846 t.addSec(dsec) 847 if t.wall&hasMonotonic != 0 { 848 te := t.ext + int64(d) 849 if d < 0 && te > t.ext || d > 0 && te < t.ext { 850 // Monotonic clock reading now out of range; degrade to wall-only. 851 t.stripMono() 852 } else { 853 t.ext = te 854 } 855 } 856 return t 857 } 858 859 // Sub returns the duration t-u. If the result exceeds the maximum (or minimum) 860 // value that can be stored in a Duration, the maximum (or minimum) duration 861 // will be returned. 862 // To compute t-d for a duration d, use t.Add(-d). 863 func (t Time) Sub(u Time) Duration { 864 if t.wall&u.wall&hasMonotonic != 0 { 865 te := t.ext 866 ue := u.ext 867 d := Duration(te - ue) 868 if d < 0 && te > ue { 869 return maxDuration // t - u is positive out of range 870 } 871 if d > 0 && te < ue { 872 return minDuration // t - u is negative out of range 873 } 874 return d 875 } 876 d := Duration(t.sec()-u.sec())*Second + Duration(t.nsec()-u.nsec()) 877 // Check for overflow or underflow. 878 switch { 879 case u.Add(d).Equal(t): 880 return d // d is correct 881 case t.Before(u): 882 return minDuration // t - u is negative out of range 883 default: 884 return maxDuration // t - u is positive out of range 885 } 886 } 887 888 // Since returns the time elapsed since t. 889 // It is shorthand for time.Now().Sub(t). 890 func Since(t Time) Duration { 891 var now Time 892 if t.wall&hasMonotonic != 0 { 893 // Common case optimization: if t has monotonic time, then Sub will use only it. 894 now = Time{hasMonotonic, runtimeNano() - startNano, nil} 895 } else { 896 now = Now() 897 } 898 return now.Sub(t) 899 } 900 901 // Until returns the duration until t. 902 // It is shorthand for t.Sub(time.Now()). 903 func Until(t Time) Duration { 904 var now Time 905 if t.wall&hasMonotonic != 0 { 906 // Common case optimization: if t has monotonic time, then Sub will use only it. 907 now = Time{hasMonotonic, runtimeNano() - startNano, nil} 908 } else { 909 now = Now() 910 } 911 return t.Sub(now) 912 } 913 914 // AddDate returns the time corresponding to adding the 915 // given number of years, months, and days to t. 916 // For example, AddDate(-1, 2, 3) applied to January 1, 2011 917 // returns March 4, 2010. 918 // 919 // AddDate normalizes its result in the same way that Date does, 920 // so, for example, adding one month to October 31 yields 921 // December 1, the normalized form for November 31. 922 func (t Time) AddDate(years int, months int, days int) Time { 923 year, month, day := t.Date() 924 hour, min, sec := t.Clock() 925 return Date(year+years, month+Month(months), day+days, hour, min, sec, int(t.nsec()), t.Location()) 926 } 927 928 const ( 929 secondsPerMinute = 60 930 secondsPerHour = 60 * secondsPerMinute 931 secondsPerDay = 24 * secondsPerHour 932 secondsPerWeek = 7 * secondsPerDay 933 daysPer400Years = 365*400 + 97 934 daysPer100Years = 365*100 + 24 935 daysPer4Years = 365*4 + 1 936 ) 937 938 // date computes the year, day of year, and when full=true, 939 // the month and day in which t occurs. 940 func (t Time) date(full bool) (year int, month Month, day int, yday int) { 941 return absDate(t.abs(), full) 942 } 943 944 // absDate is like date but operates on an absolute time. 945 func absDate(abs uint64, full bool) (year int, month Month, day int, yday int) { 946 // Split into time and day. 947 d := abs / secondsPerDay 948 949 // Account for 400 year cycles. 950 n := d / daysPer400Years 951 y := 400 * n 952 d -= daysPer400Years * n 953 954 // Cut off 100-year cycles. 955 // The last cycle has one extra leap year, so on the last day 956 // of that year, day / daysPer100Years will be 4 instead of 3. 957 // Cut it back down to 3 by subtracting n>>2. 958 n = d / daysPer100Years 959 n -= n >> 2 960 y += 100 * n 961 d -= daysPer100Years * n 962 963 // Cut off 4-year cycles. 964 // The last cycle has a missing leap year, which does not 965 // affect the computation. 966 n = d / daysPer4Years 967 y += 4 * n 968 d -= daysPer4Years * n 969 970 // Cut off years within a 4-year cycle. 971 // The last year is a leap year, so on the last day of that year, 972 // day / 365 will be 4 instead of 3. Cut it back down to 3 973 // by subtracting n>>2. 974 n = d / 365 975 n -= n >> 2 976 y += n 977 d -= 365 * n 978 979 year = int(int64(y) + absoluteZeroYear) 980 yday = int(d) 981 982 if !full { 983 return 984 } 985 986 day = yday 987 if isLeap(year) { 988 // Leap year 989 switch { 990 case day > 31+29-1: 991 // After leap day; pretend it wasn't there. 992 day-- 993 case day == 31+29-1: 994 // Leap day. 995 month = February 996 day = 29 997 return 998 } 999 } 1000 1001 // Estimate month on assumption that every month has 31 days. 1002 // The estimate may be too low by at most one month, so adjust. 1003 month = Month(day / 31) 1004 end := int(daysBefore[month+1]) 1005 var begin int 1006 if day >= end { 1007 month++ 1008 begin = end 1009 } else { 1010 begin = int(daysBefore[month]) 1011 } 1012 1013 month++ // because January is 1 1014 day = day - begin + 1 1015 return 1016 } 1017 1018 // daysBefore[m] counts the number of days in a non-leap year 1019 // before month m begins. There is an entry for m=12, counting 1020 // the number of days before January of next year (365). 1021 var daysBefore = [...]int32{ 1022 0, 1023 31, 1024 31 + 28, 1025 31 + 28 + 31, 1026 31 + 28 + 31 + 30, 1027 31 + 28 + 31 + 30 + 31, 1028 31 + 28 + 31 + 30 + 31 + 30, 1029 31 + 28 + 31 + 30 + 31 + 30 + 31, 1030 31 + 28 + 31 + 30 + 31 + 30 + 31 + 31, 1031 31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 30, 1032 31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 30 + 31, 1033 31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 30 + 31 + 30, 1034 31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 30 + 31 + 30 + 31, 1035 } 1036 1037 func daysIn(m Month, year int) int { 1038 if m == February && isLeap(year) { 1039 return 29 1040 } 1041 return int(daysBefore[m] - daysBefore[m-1]) 1042 } 1043 1044 // daysSinceEpoch takes a year and returns the number of days from 1045 // the absolute epoch to the start of that year. 1046 // This is basically (year - zeroYear) * 365, but accounting for leap days. 1047 func daysSinceEpoch(year int) uint64 { 1048 y := uint64(int64(year) - absoluteZeroYear) 1049 1050 // Add in days from 400-year cycles. 1051 n := y / 400 1052 y -= 400 * n 1053 d := daysPer400Years * n 1054 1055 // Add in 100-year cycles. 1056 n = y / 100 1057 y -= 100 * n 1058 d += daysPer100Years * n 1059 1060 // Add in 4-year cycles. 1061 n = y / 4 1062 y -= 4 * n 1063 d += daysPer4Years * n 1064 1065 // Add in non-leap years. 1066 n = y 1067 d += 365 * n 1068 1069 return d 1070 } 1071 1072 // Provided by package runtime. 1073 func now() (sec int64, nsec int32, mono int64) 1074 1075 // runtimeNano returns the current value of the runtime clock in nanoseconds. 1076 // 1077 //go:linkname runtimeNano runtime.nanotime 1078 func runtimeNano() int64 1079 1080 // Monotonic times are reported as offsets from startNano. 1081 // We initialize startNano to runtimeNano() - 1 so that on systems where 1082 // monotonic time resolution is fairly low (e.g. Windows 2008 1083 // which appears to have a default resolution of 15ms), 1084 // we avoid ever reporting a monotonic time of 0. 1085 // (Callers may want to use 0 as "time not set".) 1086 var startNano int64 = runtimeNano() - 1 1087 1088 // Now returns the current local time. 1089 func Now() Time { 1090 sec, nsec, mono := now() 1091 mono -= startNano 1092 sec += unixToInternal - minWall 1093 if uint64(sec)>>33 != 0 { 1094 return Time{uint64(nsec), sec + minWall, Local} 1095 } 1096 return Time{hasMonotonic | uint64(sec)<<nsecShift | uint64(nsec), mono, Local} 1097 } 1098 1099 func unixTime(sec int64, nsec int32) Time { 1100 return Time{uint64(nsec), sec + unixToInternal, Local} 1101 } 1102 1103 // UTC returns t with the location set to UTC. 1104 func (t Time) UTC() Time { 1105 t.setLoc(&utcLoc) 1106 return t 1107 } 1108 1109 // Local returns t with the location set to local time. 1110 func (t Time) Local() Time { 1111 t.setLoc(Local) 1112 return t 1113 } 1114 1115 // In returns a copy of t representing the same time instant, but 1116 // with the copy's location information set to loc for display 1117 // purposes. 1118 // 1119 // In panics if loc is nil. 1120 func (t Time) In(loc *Location) Time { 1121 if loc == nil { 1122 panic("time: missing Location in call to Time.In") 1123 } 1124 t.setLoc(loc) 1125 return t 1126 } 1127 1128 // Location returns the time zone information associated with t. 1129 func (t Time) Location() *Location { 1130 l := t.loc 1131 if l == nil { 1132 l = UTC 1133 } 1134 return l 1135 } 1136 1137 // Zone computes the time zone in effect at time t, returning the abbreviated 1138 // name of the zone (such as "CET") and its offset in seconds east of UTC. 1139 func (t Time) Zone() (name string, offset int) { 1140 name, offset, _, _, _ = t.loc.lookup(t.unixSec()) 1141 return 1142 } 1143 1144 // ZoneBounds returns the bounds of the time zone in effect at time t. 1145 // The zone begins at start and the next zone begins at end. 1146 // If the zone begins at the beginning of time, start will be returned as a zero Time. 1147 // If the zone goes on forever, end will be returned as a zero Time. 1148 // The Location of the returned times will be the same as t. 1149 func (t Time) ZoneBounds() (start, end Time) { 1150 _, _, startSec, endSec, _ := t.loc.lookup(t.unixSec()) 1151 if startSec != alpha { 1152 start = unixTime(startSec, 0) 1153 start.setLoc(t.loc) 1154 } 1155 if endSec != omega { 1156 end = unixTime(endSec, 0) 1157 end.setLoc(t.loc) 1158 } 1159 return 1160 } 1161 1162 // Unix returns t as a Unix time, the number of seconds elapsed 1163 // since January 1, 1970 UTC. The result does not depend on the 1164 // location associated with t. 1165 // Unix-like operating systems often record time as a 32-bit 1166 // count of seconds, but since the method here returns a 64-bit 1167 // value it is valid for billions of years into the past or future. 1168 func (t Time) Unix() int64 { 1169 return t.unixSec() 1170 } 1171 1172 // UnixMilli returns t as a Unix time, the number of milliseconds elapsed since 1173 // January 1, 1970 UTC. The result is undefined if the Unix time in 1174 // milliseconds cannot be represented by an int64 (a date more than 292 million 1175 // years before or after 1970). The result does not depend on the 1176 // location associated with t. 1177 func (t Time) UnixMilli() int64 { 1178 return t.unixSec()*1e3 + int64(t.nsec())/1e6 1179 } 1180 1181 // UnixMicro returns t as a Unix time, the number of microseconds elapsed since 1182 // January 1, 1970 UTC. The result is undefined if the Unix time in 1183 // microseconds cannot be represented by an int64 (a date before year -290307 or 1184 // after year 294246). The result does not depend on the location associated 1185 // with t. 1186 func (t Time) UnixMicro() int64 { 1187 return t.unixSec()*1e6 + int64(t.nsec())/1e3 1188 } 1189 1190 // UnixNano returns t as a Unix time, the number of nanoseconds elapsed 1191 // since January 1, 1970 UTC. The result is undefined if the Unix time 1192 // in nanoseconds cannot be represented by an int64 (a date before the year 1193 // 1678 or after 2262). Note that this means the result of calling UnixNano 1194 // on the zero Time is undefined. The result does not depend on the 1195 // location associated with t. 1196 func (t Time) UnixNano() int64 { 1197 return (t.unixSec())*1e9 + int64(t.nsec()) 1198 } 1199 1200 const ( 1201 timeBinaryVersionV1 byte = iota + 1 // For general situation 1202 timeBinaryVersionV2 // For LMT only 1203 ) 1204 1205 // MarshalBinary implements the encoding.BinaryMarshaler interface. 1206 func (t Time) MarshalBinary() ([]byte, error) { 1207 var offsetMin int16 // minutes east of UTC. -1 is UTC. 1208 var offsetSec int8 1209 version := timeBinaryVersionV1 1210 1211 if t.Location() == UTC { 1212 offsetMin = -1 1213 } else { 1214 _, offset := t.Zone() 1215 if offset%60 != 0 { 1216 version = timeBinaryVersionV2 1217 offsetSec = int8(offset % 60) 1218 } 1219 1220 offset /= 60 1221 if offset < -32768 || offset == -1 || offset > 32767 { 1222 return nil, errors.New("Time.MarshalBinary: unexpected zone offset") 1223 } 1224 offsetMin = int16(offset) 1225 } 1226 1227 sec := t.sec() 1228 nsec := t.nsec() 1229 enc := []byte{ 1230 version, // byte 0 : version 1231 byte(sec >> 56), // bytes 1-8: seconds 1232 byte(sec >> 48), 1233 byte(sec >> 40), 1234 byte(sec >> 32), 1235 byte(sec >> 24), 1236 byte(sec >> 16), 1237 byte(sec >> 8), 1238 byte(sec), 1239 byte(nsec >> 24), // bytes 9-12: nanoseconds 1240 byte(nsec >> 16), 1241 byte(nsec >> 8), 1242 byte(nsec), 1243 byte(offsetMin >> 8), // bytes 13-14: zone offset in minutes 1244 byte(offsetMin), 1245 } 1246 if version == timeBinaryVersionV2 { 1247 enc = append(enc, byte(offsetSec)) 1248 } 1249 1250 return enc, nil 1251 } 1252 1253 // UnmarshalBinary implements the encoding.BinaryUnmarshaler interface. 1254 func (t *Time) UnmarshalBinary(data []byte) error { 1255 buf := data 1256 if len(buf) == 0 { 1257 return errors.New("Time.UnmarshalBinary: no data") 1258 } 1259 1260 version := buf[0] 1261 if version != timeBinaryVersionV1 && version != timeBinaryVersionV2 { 1262 return errors.New("Time.UnmarshalBinary: unsupported version") 1263 } 1264 1265 wantLen := /*version*/ 1 + /*sec*/ 8 + /*nsec*/ 4 + /*zone offset*/ 2 1266 if version == timeBinaryVersionV2 { 1267 wantLen++ 1268 } 1269 if len(buf) != wantLen { 1270 return errors.New("Time.UnmarshalBinary: invalid length") 1271 } 1272 1273 buf = buf[1:] 1274 sec := int64(buf[7]) | int64(buf[6])<<8 | int64(buf[5])<<16 | int64(buf[4])<<24 | 1275 int64(buf[3])<<32 | int64(buf[2])<<40 | int64(buf[1])<<48 | int64(buf[0])<<56 1276 1277 buf = buf[8:] 1278 nsec := int32(buf[3]) | int32(buf[2])<<8 | int32(buf[1])<<16 | int32(buf[0])<<24 1279 1280 buf = buf[4:] 1281 offset := int(int16(buf[1])|int16(buf[0])<<8) * 60 1282 if version == timeBinaryVersionV2 { 1283 offset += int(buf[2]) 1284 } 1285 1286 *t = Time{} 1287 t.wall = uint64(nsec) 1288 t.ext = sec 1289 1290 if offset == -1*60 { 1291 t.setLoc(&utcLoc) 1292 } else if _, localoff, _, _, _ := Local.lookup(t.unixSec()); offset == localoff { 1293 t.setLoc(Local) 1294 } else { 1295 t.setLoc(FixedZone("", offset)) 1296 } 1297 1298 return nil 1299 } 1300 1301 // TODO(rsc): Remove GobEncoder, GobDecoder, MarshalJSON, UnmarshalJSON in Go 2. 1302 // The same semantics will be provided by the generic MarshalBinary, MarshalText, 1303 // UnmarshalBinary, UnmarshalText. 1304 1305 // GobEncode implements the gob.GobEncoder interface. 1306 func (t Time) GobEncode() ([]byte, error) { 1307 return t.MarshalBinary() 1308 } 1309 1310 // GobDecode implements the gob.GobDecoder interface. 1311 func (t *Time) GobDecode(data []byte) error { 1312 return t.UnmarshalBinary(data) 1313 } 1314 1315 // MarshalJSON implements the json.Marshaler interface. 1316 // The time is a quoted string in RFC 3339 format, with sub-second precision added if present. 1317 func (t Time) MarshalJSON() ([]byte, error) { 1318 if y := t.Year(); y < 0 || y >= 10000 { 1319 // RFC 3339 is clear that years are 4 digits exactly. 1320 // See golang.org/issue/4556#c15 for more discussion. 1321 return nil, errors.New("Time.MarshalJSON: year outside of range [0,9999]") 1322 } 1323 1324 b := make([]byte, 0, len(RFC3339Nano)+2) 1325 b = append(b, '"') 1326 b = t.AppendFormat(b, RFC3339Nano) 1327 b = append(b, '"') 1328 return b, nil 1329 } 1330 1331 // UnmarshalJSON implements the json.Unmarshaler interface. 1332 // The time is expected to be a quoted string in RFC 3339 format. 1333 func (t *Time) UnmarshalJSON(data []byte) error { 1334 // Ignore null, like in the main JSON package. 1335 if string(data) == "null" { 1336 return nil 1337 } 1338 // Fractional seconds are handled implicitly by Parse. 1339 var err error 1340 *t, err = Parse(`"`+RFC3339+`"`, string(data)) 1341 return err 1342 } 1343 1344 // MarshalText implements the encoding.TextMarshaler interface. 1345 // The time is formatted in RFC 3339 format, with sub-second precision added if present. 1346 func (t Time) MarshalText() ([]byte, error) { 1347 if y := t.Year(); y < 0 || y >= 10000 { 1348 return nil, errors.New("Time.MarshalText: year outside of range [0,9999]") 1349 } 1350 1351 b := make([]byte, 0, len(RFC3339Nano)) 1352 return t.AppendFormat(b, RFC3339Nano), nil 1353 } 1354 1355 // UnmarshalText implements the encoding.TextUnmarshaler interface. 1356 // The time is expected to be in RFC 3339 format. 1357 func (t *Time) UnmarshalText(data []byte) error { 1358 // Fractional seconds are handled implicitly by Parse. 1359 var err error 1360 *t, err = Parse(RFC3339, string(data)) 1361 return err 1362 } 1363 1364 // Unix returns the local Time corresponding to the given Unix time, 1365 // sec seconds and nsec nanoseconds since January 1, 1970 UTC. 1366 // It is valid to pass nsec outside the range [0, 999999999]. 1367 // Not all sec values have a corresponding time value. One such 1368 // value is 1<<63-1 (the largest int64 value). 1369 func Unix(sec int64, nsec int64) Time { 1370 if nsec < 0 || nsec >= 1e9 { 1371 n := nsec / 1e9 1372 sec += n 1373 nsec -= n * 1e9 1374 if nsec < 0 { 1375 nsec += 1e9 1376 sec-- 1377 } 1378 } 1379 return unixTime(sec, int32(nsec)) 1380 } 1381 1382 // UnixMilli returns the local Time corresponding to the given Unix time, 1383 // msec milliseconds since January 1, 1970 UTC. 1384 func UnixMilli(msec int64) Time { 1385 return Unix(msec/1e3, (msec%1e3)*1e6) 1386 } 1387 1388 // UnixMicro returns the local Time corresponding to the given Unix time, 1389 // usec microseconds since January 1, 1970 UTC. 1390 func UnixMicro(usec int64) Time { 1391 return Unix(usec/1e6, (usec%1e6)*1e3) 1392 } 1393 1394 // IsDST reports whether the time in the configured location is in Daylight Savings Time. 1395 func (t Time) IsDST() bool { 1396 _, _, _, _, isDST := t.loc.lookup(t.Unix()) 1397 return isDST 1398 } 1399 1400 func isLeap(year int) bool { 1401 return year%4 == 0 && (year%100 != 0 || year%400 == 0) 1402 } 1403 1404 // norm returns nhi, nlo such that 1405 // 1406 // hi * base + lo == nhi * base + nlo 1407 // 0 <= nlo < base 1408 func norm(hi, lo, base int) (nhi, nlo int) { 1409 if lo < 0 { 1410 n := (-lo-1)/base + 1 1411 hi -= n 1412 lo += n * base 1413 } 1414 if lo >= base { 1415 n := lo / base 1416 hi += n 1417 lo -= n * base 1418 } 1419 return hi, lo 1420 } 1421 1422 // Date returns the Time corresponding to 1423 // 1424 // yyyy-mm-dd hh:mm:ss + nsec nanoseconds 1425 // 1426 // in the appropriate zone for that time in the given location. 1427 // 1428 // The month, day, hour, min, sec, and nsec values may be outside 1429 // their usual ranges and will be normalized during the conversion. 1430 // For example, October 32 converts to November 1. 1431 // 1432 // A daylight savings time transition skips or repeats times. 1433 // For example, in the United States, March 13, 2011 2:15am never occurred, 1434 // while November 6, 2011 1:15am occurred twice. In such cases, the 1435 // choice of time zone, and therefore the time, is not well-defined. 1436 // Date returns a time that is correct in one of the two zones involved 1437 // in the transition, but it does not guarantee which. 1438 // 1439 // Date panics if loc is nil. 1440 func Date(year int, month Month, day, hour, min, sec, nsec int, loc *Location) Time { 1441 if loc == nil { 1442 panic("time: missing Location in call to Date") 1443 } 1444 1445 // Normalize month, overflowing into year. 1446 m := int(month) - 1 1447 year, m = norm(year, m, 12) 1448 month = Month(m) + 1 1449 1450 // Normalize nsec, sec, min, hour, overflowing into day. 1451 sec, nsec = norm(sec, nsec, 1e9) 1452 min, sec = norm(min, sec, 60) 1453 hour, min = norm(hour, min, 60) 1454 day, hour = norm(day, hour, 24) 1455 1456 // Compute days since the absolute epoch. 1457 d := daysSinceEpoch(year) 1458 1459 // Add in days before this month. 1460 d += uint64(daysBefore[month-1]) 1461 if isLeap(year) && month >= March { 1462 d++ // February 29 1463 } 1464 1465 // Add in days before today. 1466 d += uint64(day - 1) 1467 1468 // Add in time elapsed today. 1469 abs := d * secondsPerDay 1470 abs += uint64(hour*secondsPerHour + min*secondsPerMinute + sec) 1471 1472 unix := int64(abs) + (absoluteToInternal + internalToUnix) 1473 1474 // Look for zone offset for expected time, so we can adjust to UTC. 1475 // The lookup function expects UTC, so first we pass unix in the 1476 // hope that it will not be too close to a zone transition, 1477 // and then adjust if it is. 1478 _, offset, start, end, _ := loc.lookup(unix) 1479 if offset != 0 { 1480 utc := unix - int64(offset) 1481 // If utc is valid for the time zone we found, then we have the right offset. 1482 // If not, we get the correct offset by looking up utc in the location. 1483 if utc < start || utc >= end { 1484 _, offset, _, _, _ = loc.lookup(utc) 1485 } 1486 unix -= int64(offset) 1487 } 1488 1489 t := unixTime(unix, int32(nsec)) 1490 t.setLoc(loc) 1491 return t 1492 } 1493 1494 // Truncate returns the result of rounding t down to a multiple of d (since the zero time). 1495 // If d <= 0, Truncate returns t stripped of any monotonic clock reading but otherwise unchanged. 1496 // 1497 // Truncate operates on the time as an absolute duration since the 1498 // zero time; it does not operate on the presentation form of the 1499 // time. Thus, Truncate(Hour) may return a time with a non-zero 1500 // minute, depending on the time's Location. 1501 func (t Time) Truncate(d Duration) Time { 1502 t.stripMono() 1503 if d <= 0 { 1504 return t 1505 } 1506 _, r := div(t, d) 1507 return t.Add(-r) 1508 } 1509 1510 // Round returns the result of rounding t to the nearest multiple of d (since the zero time). 1511 // The rounding behavior for halfway values is to round up. 1512 // If d <= 0, Round returns t stripped of any monotonic clock reading but otherwise unchanged. 1513 // 1514 // Round operates on the time as an absolute duration since the 1515 // zero time; it does not operate on the presentation form of the 1516 // time. Thus, Round(Hour) may return a time with a non-zero 1517 // minute, depending on the time's Location. 1518 func (t Time) Round(d Duration) Time { 1519 t.stripMono() 1520 if d <= 0 { 1521 return t 1522 } 1523 _, r := div(t, d) 1524 if lessThanHalf(r, d) { 1525 return t.Add(-r) 1526 } 1527 return t.Add(d - r) 1528 } 1529 1530 // div divides t by d and returns the quotient parity and remainder. 1531 // We don't use the quotient parity anymore (round half up instead of round to even) 1532 // but it's still here in case we change our minds. 1533 func div(t Time, d Duration) (qmod2 int, r Duration) { 1534 neg := false 1535 nsec := t.nsec() 1536 sec := t.sec() 1537 if sec < 0 { 1538 // Operate on absolute value. 1539 neg = true 1540 sec = -sec 1541 nsec = -nsec 1542 if nsec < 0 { 1543 nsec += 1e9 1544 sec-- // sec >= 1 before the -- so safe 1545 } 1546 } 1547 1548 switch { 1549 // Special case: 2d divides 1 second. 1550 case d < Second && Second%(d+d) == 0: 1551 qmod2 = int(nsec/int32(d)) & 1 1552 r = Duration(nsec % int32(d)) 1553 1554 // Special case: d is a multiple of 1 second. 1555 case d%Second == 0: 1556 d1 := int64(d / Second) 1557 qmod2 = int(sec/d1) & 1 1558 r = Duration(sec%d1)*Second + Duration(nsec) 1559 1560 // General case. 1561 // This could be faster if more cleverness were applied, 1562 // but it's really only here to avoid special case restrictions in the API. 1563 // No one will care about these cases. 1564 default: 1565 // Compute nanoseconds as 128-bit number. 1566 sec := uint64(sec) 1567 tmp := (sec >> 32) * 1e9 1568 u1 := tmp >> 32 1569 u0 := tmp << 32 1570 tmp = (sec & 0xFFFFFFFF) * 1e9 1571 u0x, u0 := u0, u0+tmp 1572 if u0 < u0x { 1573 u1++ 1574 } 1575 u0x, u0 = u0, u0+uint64(nsec) 1576 if u0 < u0x { 1577 u1++ 1578 } 1579 1580 // Compute remainder by subtracting r<<k for decreasing k. 1581 // Quotient parity is whether we subtract on last round. 1582 d1 := uint64(d) 1583 for d1>>63 != 1 { 1584 d1 <<= 1 1585 } 1586 d0 := uint64(0) 1587 for { 1588 qmod2 = 0 1589 if u1 > d1 || u1 == d1 && u0 >= d0 { 1590 // subtract 1591 qmod2 = 1 1592 u0x, u0 = u0, u0-d0 1593 if u0 > u0x { 1594 u1-- 1595 } 1596 u1 -= d1 1597 } 1598 if d1 == 0 && d0 == uint64(d) { 1599 break 1600 } 1601 d0 >>= 1 1602 d0 |= (d1 & 1) << 63 1603 d1 >>= 1 1604 } 1605 r = Duration(u0) 1606 } 1607 1608 if neg && r != 0 { 1609 // If input was negative and not an exact multiple of d, we computed q, r such that 1610 // q*d + r = -t 1611 // But the right answers are given by -(q-1), d-r: 1612 // q*d + r = -t 1613 // -q*d - r = t 1614 // -(q-1)*d + (d - r) = t 1615 qmod2 ^= 1 1616 r = d - r 1617 } 1618 return 1619 } 1620