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 // Note that the Go == operator compares not just the time instant but 68 // also the Location and the monotonic clock reading. See the 69 // documentation for the Time type for a discussion of equality 70 // testing for Time values. 71 // 72 // For debugging, the result of t.String does include the monotonic 73 // clock reading if present. If t != u because of different monotonic clock readings, 74 // that difference will be visible when printing t.String() and u.String(). 75 // 76 package time 77 78 import ( 79 "errors" 80 _ "unsafe" // for go:linkname 81 ) 82 83 // A Time represents an instant in time with nanosecond precision. 84 // 85 // Programs using times should typically store and pass them as values, 86 // not pointers. That is, time variables and struct fields should be of 87 // type time.Time, not *time.Time. 88 // 89 // A Time value can be used by multiple goroutines simultaneously except 90 // that the methods GobDecode, UnmarshalBinary, UnmarshalJSON and 91 // UnmarshalText are not concurrency-safe. 92 // 93 // Time instants can be compared using the Before, After, and Equal methods. 94 // The Sub method subtracts two instants, producing a Duration. 95 // The Add method adds a Time and a Duration, producing a Time. 96 // 97 // The zero value of type Time is January 1, year 1, 00:00:00.000000000 UTC. 98 // As this time is unlikely to come up in practice, the IsZero method gives 99 // a simple way of detecting a time that has not been initialized explicitly. 100 // 101 // Each Time has associated with it a Location, consulted when computing the 102 // presentation form of the time, such as in the Format, Hour, and Year methods. 103 // The methods Local, UTC, and In return a Time with a specific location. 104 // Changing the location in this way changes only the presentation; it does not 105 // change the instant in time being denoted and therefore does not affect the 106 // computations described in earlier paragraphs. 107 // 108 // Representations of a Time value saved by the GobEncode, MarshalBinary, 109 // MarshalJSON, and MarshalText methods store the Time.Location's offset, but not 110 // the location name. They therefore lose information about Daylight Saving Time. 111 // 112 // In addition to the required “wall clock” reading, a Time may contain an optional 113 // reading of the current process's monotonic clock, to provide additional precision 114 // for comparison or subtraction. 115 // See the “Monotonic Clocks” section in the package documentation for details. 116 // 117 // Note that the Go == operator compares not just the time instant but also the 118 // Location and the monotonic clock reading. Therefore, Time values should not 119 // be used as map or database keys without first guaranteeing that the 120 // identical Location has been set for all values, which can be achieved 121 // through use of the UTC or Local method, and that the monotonic clock reading 122 // has been stripped by setting t = t.Round(0). In general, prefer t.Equal(u) 123 // to t == u, since t.Equal uses the most accurate comparison available and 124 // correctly handles the case when only one of its arguments has a monotonic 125 // clock reading. 126 // 127 type Time struct { 128 // wall and ext encode the wall time seconds, wall time nanoseconds, 129 // and optional monotonic clock reading in nanoseconds. 130 // 131 // From high to low bit position, wall encodes a 1-bit flag (hasMonotonic), 132 // a 33-bit seconds field, and a 30-bit wall time nanoseconds field. 133 // The nanoseconds field is in the range [0, 999999999]. 134 // If the hasMonotonic bit is 0, then the 33-bit field must be zero 135 // and the full signed 64-bit wall seconds since Jan 1 year 1 is stored in ext. 136 // If the hasMonotonic bit is 1, then the 33-bit field holds a 33-bit 137 // unsigned wall seconds since Jan 1 year 1885, and ext holds a 138 // signed 64-bit monotonic clock reading, nanoseconds since process start. 139 wall uint64 140 ext int64 141 142 // loc specifies the Location that should be used to 143 // determine the minute, hour, month, day, and year 144 // that correspond to this Time. 145 // The nil location means UTC. 146 // All UTC times are represented with loc==nil, never loc==&utcLoc. 147 loc *Location 148 } 149 150 const ( 151 hasMonotonic = 1 << 63 152 maxWall = wallToInternal + (1<<33 - 1) // year 2157 153 minWall = wallToInternal // year 1885 154 nsecMask = 1<<30 - 1 155 nsecShift = 30 156 ) 157 158 // These helpers for manipulating the wall and monotonic clock readings 159 // take pointer receivers, even when they don't modify the time, 160 // to make them cheaper to call. 161 162 // nsec returns the time's nanoseconds. 163 func (t *Time) nsec() int32 { 164 return int32(t.wall & nsecMask) 165 } 166 167 // sec returns the time's seconds since Jan 1 year 1. 168 func (t *Time) sec() int64 { 169 if t.wall&hasMonotonic != 0 { 170 return wallToInternal + int64(t.wall<<1>>(nsecShift+1)) 171 } 172 return t.ext 173 } 174 175 // unixSec returns the time's seconds since Jan 1 1970 (Unix time). 176 func (t *Time) unixSec() int64 { return t.sec() + internalToUnix } 177 178 // addSec adds d seconds to the time. 179 func (t *Time) addSec(d int64) { 180 if t.wall&hasMonotonic != 0 { 181 sec := int64(t.wall << 1 >> (nsecShift + 1)) 182 dsec := sec + d 183 if 0 <= dsec && dsec <= 1<<33-1 { 184 t.wall = t.wall&nsecMask | uint64(dsec)<<nsecShift | hasMonotonic 185 return 186 } 187 // Wall second now out of range for packed field. 188 // Move to ext. 189 t.stripMono() 190 } 191 192 // Check if the sum of t.ext and d overflows and handle it properly. 193 sum := t.ext + d 194 if (sum > t.ext) == (d > 0) { 195 t.ext = sum 196 } else if d > 0 { 197 t.ext = 1<<63 - 1 198 } else { 199 t.ext = -(1<<63 - 1) 200 } 201 } 202 203 // setLoc sets the location associated with the time. 204 func (t *Time) setLoc(loc *Location) { 205 if loc == &utcLoc { 206 loc = nil 207 } 208 t.stripMono() 209 t.loc = loc 210 } 211 212 // stripMono strips the monotonic clock reading in t. 213 func (t *Time) stripMono() { 214 if t.wall&hasMonotonic != 0 { 215 t.ext = t.sec() 216 t.wall &= nsecMask 217 } 218 } 219 220 // setMono sets the monotonic clock reading in t. 221 // If t cannot hold a monotonic clock reading, 222 // because its wall time is too large, 223 // setMono is a no-op. 224 func (t *Time) setMono(m int64) { 225 if t.wall&hasMonotonic == 0 { 226 sec := t.ext 227 if sec < minWall || maxWall < sec { 228 return 229 } 230 t.wall |= hasMonotonic | uint64(sec-minWall)<<nsecShift 231 } 232 t.ext = m 233 } 234 235 // mono returns t's monotonic clock reading. 236 // It returns 0 for a missing reading. 237 // This function is used only for testing, 238 // so it's OK that technically 0 is a valid 239 // monotonic clock reading as well. 240 func (t *Time) mono() int64 { 241 if t.wall&hasMonotonic == 0 { 242 return 0 243 } 244 return t.ext 245 } 246 247 // After reports whether the time instant t is after u. 248 func (t Time) After(u Time) bool { 249 if t.wall&u.wall&hasMonotonic != 0 { 250 return t.ext > u.ext 251 } 252 ts := t.sec() 253 us := u.sec() 254 return ts > us || ts == us && t.nsec() > u.nsec() 255 } 256 257 // Before reports whether the time instant t is before u. 258 func (t Time) Before(u Time) bool { 259 if t.wall&u.wall&hasMonotonic != 0 { 260 return t.ext < u.ext 261 } 262 ts := t.sec() 263 us := u.sec() 264 return ts < us || ts == us && t.nsec() < u.nsec() 265 } 266 267 // Equal reports whether t and u represent the same time instant. 268 // Two times can be equal even if they are in different locations. 269 // For example, 6:00 +0200 and 4:00 UTC are Equal. 270 // See the documentation on the Time type for the pitfalls of using == with 271 // Time values; most code should use Equal instead. 272 func (t Time) Equal(u Time) bool { 273 if t.wall&u.wall&hasMonotonic != 0 { 274 return t.ext == u.ext 275 } 276 return t.sec() == u.sec() && t.nsec() == u.nsec() 277 } 278 279 // A Month specifies a month of the year (January = 1, ...). 280 type Month int 281 282 const ( 283 January Month = 1 + iota 284 February 285 March 286 April 287 May 288 June 289 July 290 August 291 September 292 October 293 November 294 December 295 ) 296 297 // String returns the English name of the month ("January", "February", ...). 298 func (m Month) String() string { 299 if January <= m && m <= December { 300 return longMonthNames[m-1] 301 } 302 buf := make([]byte, 20) 303 n := fmtInt(buf, uint64(m)) 304 return "%!Month(" + string(buf[n:]) + ")" 305 } 306 307 // A Weekday specifies a day of the week (Sunday = 0, ...). 308 type Weekday int 309 310 const ( 311 Sunday Weekday = iota 312 Monday 313 Tuesday 314 Wednesday 315 Thursday 316 Friday 317 Saturday 318 ) 319 320 // String returns the English name of the day ("Sunday", "Monday", ...). 321 func (d Weekday) String() string { 322 if Sunday <= d && d <= Saturday { 323 return longDayNames[d] 324 } 325 buf := make([]byte, 20) 326 n := fmtInt(buf, uint64(d)) 327 return "%!Weekday(" + string(buf[n:]) + ")" 328 } 329 330 // Computations on time. 331 // 332 // The zero value for a Time is defined to be 333 // January 1, year 1, 00:00:00.000000000 UTC 334 // which (1) looks like a zero, or as close as you can get in a date 335 // (1-1-1 00:00:00 UTC), (2) is unlikely enough to arise in practice to 336 // be a suitable "not set" sentinel, unlike Jan 1 1970, and (3) has a 337 // non-negative year even in time zones west of UTC, unlike 1-1-0 338 // 00:00:00 UTC, which would be 12-31-(-1) 19:00:00 in New York. 339 // 340 // The zero Time value does not force a specific epoch for the time 341 // representation. For example, to use the Unix epoch internally, we 342 // could define that to distinguish a zero value from Jan 1 1970, that 343 // time would be represented by sec=-1, nsec=1e9. However, it does 344 // suggest a representation, namely using 1-1-1 00:00:00 UTC as the 345 // epoch, and that's what we do. 346 // 347 // The Add and Sub computations are oblivious to the choice of epoch. 348 // 349 // The presentation computations - year, month, minute, and so on - all 350 // rely heavily on division and modulus by positive constants. For 351 // calendrical calculations we want these divisions to round down, even 352 // for negative values, so that the remainder is always positive, but 353 // Go's division (like most hardware division instructions) rounds to 354 // zero. We can still do those computations and then adjust the result 355 // for a negative numerator, but it's annoying to write the adjustment 356 // over and over. Instead, we can change to a different epoch so long 357 // ago that all the times we care about will be positive, and then round 358 // to zero and round down coincide. These presentation routines already 359 // have to add the zone offset, so adding the translation to the 360 // alternate epoch is cheap. For example, having a non-negative time t 361 // means that we can write 362 // 363 // sec = t % 60 364 // 365 // instead of 366 // 367 // sec = t % 60 368 // if sec < 0 { 369 // sec += 60 370 // } 371 // 372 // everywhere. 373 // 374 // The calendar runs on an exact 400 year cycle: a 400-year calendar 375 // printed for 1970-2369 will apply as well to 2370-2769. Even the days 376 // of the week match up. It simplifies the computations to choose the 377 // cycle boundaries so that the exceptional years are always delayed as 378 // long as possible. That means choosing a year equal to 1 mod 400, so 379 // that the first leap year is the 4th year, the first missed leap year 380 // is the 100th year, and the missed missed leap year is the 400th year. 381 // So we'd prefer instead to print a calendar for 2001-2400 and reuse it 382 // for 2401-2800. 383 // 384 // Finally, it's convenient if the delta between the Unix epoch and 385 // long-ago epoch is representable by an int64 constant. 386 // 387 // These three considerations—choose an epoch as early as possible, that 388 // uses a year equal to 1 mod 400, and that is no more than 2⁶³ seconds 389 // earlier than 1970—bring us to the year -292277022399. We refer to 390 // this year as the absolute zero year, and to times measured as a uint64 391 // seconds since this year as absolute times. 392 // 393 // Times measured as an int64 seconds since the year 1—the representation 394 // used for Time's sec field—are called internal times. 395 // 396 // Times measured as an int64 seconds since the year 1970 are called Unix 397 // times. 398 // 399 // It is tempting to just use the year 1 as the absolute epoch, defining 400 // that the routines are only valid for years >= 1. However, the 401 // routines would then be invalid when displaying the epoch in time zones 402 // west of UTC, since it is year 0. It doesn't seem tenable to say that 403 // printing the zero time correctly isn't supported in half the time 404 // zones. By comparison, it's reasonable to mishandle some times in 405 // the year -292277022399. 406 // 407 // All this is opaque to clients of the API and can be changed if a 408 // better implementation presents itself. 409 410 const ( 411 // The unsigned zero year for internal calculations. 412 // Must be 1 mod 400, and times before it will not compute correctly, 413 // but otherwise can be changed at will. 414 absoluteZeroYear = -292277022399 415 416 // The year of the zero Time. 417 // Assumed by the unixToInternal computation below. 418 internalYear = 1 419 420 // Offsets to convert between internal and absolute or Unix times. 421 absoluteToInternal int64 = (absoluteZeroYear - internalYear) * 365.2425 * secondsPerDay 422 internalToAbsolute = -absoluteToInternal 423 424 unixToInternal int64 = (1969*365 + 1969/4 - 1969/100 + 1969/400) * secondsPerDay 425 internalToUnix int64 = -unixToInternal 426 427 wallToInternal int64 = (1884*365 + 1884/4 - 1884/100 + 1884/400) * secondsPerDay 428 internalToWall int64 = -wallToInternal 429 ) 430 431 // IsZero reports whether t represents the zero time instant, 432 // January 1, year 1, 00:00:00 UTC. 433 func (t Time) IsZero() bool { 434 return t.sec() == 0 && t.nsec() == 0 435 } 436 437 // abs returns the time t as an absolute time, adjusted by the zone offset. 438 // It is called when computing a presentation property like Month or Hour. 439 func (t Time) abs() uint64 { 440 l := t.loc 441 // Avoid function calls when possible. 442 if l == nil || l == &localLoc { 443 l = l.get() 444 } 445 sec := t.unixSec() 446 if l != &utcLoc { 447 if l.cacheZone != nil && l.cacheStart <= sec && sec < l.cacheEnd { 448 sec += int64(l.cacheZone.offset) 449 } else { 450 _, offset, _, _, _ := l.lookup(sec) 451 sec += int64(offset) 452 } 453 } 454 return uint64(sec + (unixToInternal + internalToAbsolute)) 455 } 456 457 // locabs is a combination of the Zone and abs methods, 458 // extracting both return values from a single zone lookup. 459 func (t Time) locabs() (name string, offset int, abs uint64) { 460 l := t.loc 461 if l == nil || l == &localLoc { 462 l = l.get() 463 } 464 // Avoid function call if we hit the local time cache. 465 sec := t.unixSec() 466 if l != &utcLoc { 467 if l.cacheZone != nil && l.cacheStart <= sec && sec < l.cacheEnd { 468 name = l.cacheZone.name 469 offset = l.cacheZone.offset 470 } else { 471 name, offset, _, _, _ = l.lookup(sec) 472 } 473 sec += int64(offset) 474 } else { 475 name = "UTC" 476 } 477 abs = uint64(sec + (unixToInternal + internalToAbsolute)) 478 return 479 } 480 481 // Date returns the year, month, and day in which t occurs. 482 func (t Time) Date() (year int, month Month, day int) { 483 year, month, day, _ = t.date(true) 484 return 485 } 486 487 // Year returns the year in which t occurs. 488 func (t Time) Year() int { 489 year, _, _, _ := t.date(false) 490 return year 491 } 492 493 // Month returns the month of the year specified by t. 494 func (t Time) Month() Month { 495 _, month, _, _ := t.date(true) 496 return month 497 } 498 499 // Day returns the day of the month specified by t. 500 func (t Time) Day() int { 501 _, _, day, _ := t.date(true) 502 return day 503 } 504 505 // Weekday returns the day of the week specified by t. 506 func (t Time) Weekday() Weekday { 507 return absWeekday(t.abs()) 508 } 509 510 // absWeekday is like Weekday but operates on an absolute time. 511 func absWeekday(abs uint64) Weekday { 512 // January 1 of the absolute year, like January 1 of 2001, was a Monday. 513 sec := (abs + uint64(Monday)*secondsPerDay) % secondsPerWeek 514 return Weekday(int(sec) / secondsPerDay) 515 } 516 517 // ISOWeek returns the ISO 8601 year and week number in which t occurs. 518 // Week ranges from 1 to 53. Jan 01 to Jan 03 of year n might belong to 519 // week 52 or 53 of year n-1, and Dec 29 to Dec 31 might belong to week 1 520 // of year n+1. 521 func (t Time) ISOWeek() (year, week int) { 522 // According to the rule that the first calendar week of a calendar year is 523 // the week including the first Thursday of that year, and that the last one is 524 // the week immediately preceding the first calendar week of the next calendar year. 525 // See https://www.iso.org/obp/ui#iso:std:iso:8601:-1:ed-1:v1:en:term:3.1.1.23 for details. 526 527 // weeks start with Monday 528 // Monday Tuesday Wednesday Thursday Friday Saturday Sunday 529 // 1 2 3 4 5 6 7 530 // +3 +2 +1 0 -1 -2 -3 531 // the offset to Thursday 532 abs := t.abs() 533 d := Thursday - absWeekday(abs) 534 // handle Sunday 535 if d == 4 { 536 d = -3 537 } 538 // find the Thursday of the calendar week 539 abs += uint64(d) * secondsPerDay 540 year, _, _, yday := absDate(abs, false) 541 return year, yday/7 + 1 542 } 543 544 // Clock returns the hour, minute, and second within the day specified by t. 545 func (t Time) Clock() (hour, min, sec int) { 546 return absClock(t.abs()) 547 } 548 549 // absClock is like clock but operates on an absolute time. 550 func absClock(abs uint64) (hour, min, sec int) { 551 sec = int(abs % secondsPerDay) 552 hour = sec / secondsPerHour 553 sec -= hour * secondsPerHour 554 min = sec / secondsPerMinute 555 sec -= min * secondsPerMinute 556 return 557 } 558 559 // Hour returns the hour within the day specified by t, in the range [0, 23]. 560 func (t Time) Hour() int { 561 return int(t.abs()%secondsPerDay) / secondsPerHour 562 } 563 564 // Minute returns the minute offset within the hour specified by t, in the range [0, 59]. 565 func (t Time) Minute() int { 566 return int(t.abs()%secondsPerHour) / secondsPerMinute 567 } 568 569 // Second returns the second offset within the minute specified by t, in the range [0, 59]. 570 func (t Time) Second() int { 571 return int(t.abs() % secondsPerMinute) 572 } 573 574 // Nanosecond returns the nanosecond offset within the second specified by t, 575 // in the range [0, 999999999]. 576 func (t Time) Nanosecond() int { 577 return int(t.nsec()) 578 } 579 580 // YearDay returns the day of the year specified by t, in the range [1,365] for non-leap years, 581 // and [1,366] in leap years. 582 func (t Time) YearDay() int { 583 _, _, _, yday := t.date(false) 584 return yday + 1 585 } 586 587 // A Duration represents the elapsed time between two instants 588 // as an int64 nanosecond count. The representation limits the 589 // largest representable duration to approximately 290 years. 590 type Duration int64 591 592 const ( 593 minDuration Duration = -1 << 63 594 maxDuration Duration = 1<<63 - 1 595 ) 596 597 // Common durations. There is no definition for units of Day or larger 598 // to avoid confusion across daylight savings time zone transitions. 599 // 600 // To count the number of units in a Duration, divide: 601 // second := time.Second 602 // fmt.Print(int64(second/time.Millisecond)) // prints 1000 603 // 604 // To convert an integer number of units to a Duration, multiply: 605 // seconds := 10 606 // fmt.Print(time.Duration(seconds)*time.Second) // prints 10s 607 // 608 const ( 609 Nanosecond Duration = 1 610 Microsecond = 1000 * Nanosecond 611 Millisecond = 1000 * Microsecond 612 Second = 1000 * Millisecond 613 Minute = 60 * Second 614 Hour = 60 * Minute 615 ) 616 617 // String returns a string representing the duration in the form "72h3m0.5s". 618 // Leading zero units are omitted. As a special case, durations less than one 619 // second format use a smaller unit (milli-, micro-, or nanoseconds) to ensure 620 // that the leading digit is non-zero. The zero duration formats as 0s. 621 func (d Duration) String() string { 622 // Largest time is 2540400h10m10.000000000s 623 var buf [32]byte 624 w := len(buf) 625 626 u := uint64(d) 627 neg := d < 0 628 if neg { 629 u = -u 630 } 631 632 if u < uint64(Second) { 633 // Special case: if duration is smaller than a second, 634 // use smaller units, like 1.2ms 635 var prec int 636 w-- 637 buf[w] = 's' 638 w-- 639 switch { 640 case u == 0: 641 return "0s" 642 case u < uint64(Microsecond): 643 // print nanoseconds 644 prec = 0 645 buf[w] = 'n' 646 case u < uint64(Millisecond): 647 // print microseconds 648 prec = 3 649 // U+00B5 'µ' micro sign == 0xC2 0xB5 650 w-- // Need room for two bytes. 651 copy(buf[w:], "µ") 652 default: 653 // print milliseconds 654 prec = 6 655 buf[w] = 'm' 656 } 657 w, u = fmtFrac(buf[:w], u, prec) 658 w = fmtInt(buf[:w], u) 659 } else { 660 w-- 661 buf[w] = 's' 662 663 w, u = fmtFrac(buf[:w], u, 9) 664 665 // u is now integer seconds 666 w = fmtInt(buf[:w], u%60) 667 u /= 60 668 669 // u is now integer minutes 670 if u > 0 { 671 w-- 672 buf[w] = 'm' 673 w = fmtInt(buf[:w], u%60) 674 u /= 60 675 676 // u is now integer hours 677 // Stop at hours because days can be different lengths. 678 if u > 0 { 679 w-- 680 buf[w] = 'h' 681 w = fmtInt(buf[:w], u) 682 } 683 } 684 } 685 686 if neg { 687 w-- 688 buf[w] = '-' 689 } 690 691 return string(buf[w:]) 692 } 693 694 // fmtFrac formats the fraction of v/10**prec (e.g., ".12345") into the 695 // tail of buf, omitting trailing zeros. It omits the decimal 696 // point too when the fraction is 0. It returns the index where the 697 // output bytes begin and the value v/10**prec. 698 func fmtFrac(buf []byte, v uint64, prec int) (nw int, nv uint64) { 699 // Omit trailing zeros up to and including decimal point. 700 w := len(buf) 701 print := false 702 for i := 0; i < prec; i++ { 703 digit := v % 10 704 print = print || digit != 0 705 if print { 706 w-- 707 buf[w] = byte(digit) + '0' 708 } 709 v /= 10 710 } 711 if print { 712 w-- 713 buf[w] = '.' 714 } 715 return w, v 716 } 717 718 // fmtInt formats v into the tail of buf. 719 // It returns the index where the output begins. 720 func fmtInt(buf []byte, v uint64) int { 721 w := len(buf) 722 if v == 0 { 723 w-- 724 buf[w] = '0' 725 } else { 726 for v > 0 { 727 w-- 728 buf[w] = byte(v%10) + '0' 729 v /= 10 730 } 731 } 732 return w 733 } 734 735 // Nanoseconds returns the duration as an integer nanosecond count. 736 func (d Duration) Nanoseconds() int64 { return int64(d) } 737 738 // Microseconds returns the duration as an integer microsecond count. 739 func (d Duration) Microseconds() int64 { return int64(d) / 1e3 } 740 741 // Milliseconds returns the duration as an integer millisecond count. 742 func (d Duration) Milliseconds() int64 { return int64(d) / 1e6 } 743 744 // These methods return float64 because the dominant 745 // use case is for printing a floating point number like 1.5s, and 746 // a truncation to integer would make them not useful in those cases. 747 // Splitting the integer and fraction ourselves guarantees that 748 // converting the returned float64 to an integer rounds the same 749 // way that a pure integer conversion would have, even in cases 750 // where, say, float64(d.Nanoseconds())/1e9 would have rounded 751 // differently. 752 753 // Seconds returns the duration as a floating point number of seconds. 754 func (d Duration) Seconds() float64 { 755 sec := d / Second 756 nsec := d % Second 757 return float64(sec) + float64(nsec)/1e9 758 } 759 760 // Minutes returns the duration as a floating point number of minutes. 761 func (d Duration) Minutes() float64 { 762 min := d / Minute 763 nsec := d % Minute 764 return float64(min) + float64(nsec)/(60*1e9) 765 } 766 767 // Hours returns the duration as a floating point number of hours. 768 func (d Duration) Hours() float64 { 769 hour := d / Hour 770 nsec := d % Hour 771 return float64(hour) + float64(nsec)/(60*60*1e9) 772 } 773 774 // Truncate returns the result of rounding d toward zero to a multiple of m. 775 // If m <= 0, Truncate returns d unchanged. 776 func (d Duration) Truncate(m Duration) Duration { 777 if m <= 0 { 778 return d 779 } 780 return d - d%m 781 } 782 783 // lessThanHalf reports whether x+x < y but avoids overflow, 784 // assuming x and y are both positive (Duration is signed). 785 func lessThanHalf(x, y Duration) bool { 786 return uint64(x)+uint64(x) < uint64(y) 787 } 788 789 // Round returns the result of rounding d to the nearest multiple of m. 790 // The rounding behavior for halfway values is to round away from zero. 791 // If the result exceeds the maximum (or minimum) 792 // value that can be stored in a Duration, 793 // Round returns the maximum (or minimum) duration. 794 // If m <= 0, Round returns d unchanged. 795 func (d Duration) Round(m Duration) Duration { 796 if m <= 0 { 797 return d 798 } 799 r := d % m 800 if d < 0 { 801 r = -r 802 if lessThanHalf(r, m) { 803 return d + r 804 } 805 if d1 := d - m + r; d1 < d { 806 return d1 807 } 808 return minDuration // overflow 809 } 810 if lessThanHalf(r, m) { 811 return d - r 812 } 813 if d1 := d + m - r; d1 > d { 814 return d1 815 } 816 return maxDuration // overflow 817 } 818 819 // Add returns the time t+d. 820 func (t Time) Add(d Duration) Time { 821 dsec := int64(d / 1e9) 822 nsec := t.nsec() + int32(d%1e9) 823 if nsec >= 1e9 { 824 dsec++ 825 nsec -= 1e9 826 } else if nsec < 0 { 827 dsec-- 828 nsec += 1e9 829 } 830 t.wall = t.wall&^nsecMask | uint64(nsec) // update nsec 831 t.addSec(dsec) 832 if t.wall&hasMonotonic != 0 { 833 te := t.ext + int64(d) 834 if d < 0 && te > t.ext || d > 0 && te < t.ext { 835 // Monotonic clock reading now out of range; degrade to wall-only. 836 t.stripMono() 837 } else { 838 t.ext = te 839 } 840 } 841 return t 842 } 843 844 // Sub returns the duration t-u. If the result exceeds the maximum (or minimum) 845 // value that can be stored in a Duration, the maximum (or minimum) duration 846 // will be returned. 847 // To compute t-d for a duration d, use t.Add(-d). 848 func (t Time) Sub(u Time) Duration { 849 if t.wall&u.wall&hasMonotonic != 0 { 850 te := t.ext 851 ue := u.ext 852 d := Duration(te - ue) 853 if d < 0 && te > ue { 854 return maxDuration // t - u is positive out of range 855 } 856 if d > 0 && te < ue { 857 return minDuration // t - u is negative out of range 858 } 859 return d 860 } 861 d := Duration(t.sec()-u.sec())*Second + Duration(t.nsec()-u.nsec()) 862 // Check for overflow or underflow. 863 switch { 864 case u.Add(d).Equal(t): 865 return d // d is correct 866 case t.Before(u): 867 return minDuration // t - u is negative out of range 868 default: 869 return maxDuration // t - u is positive out of range 870 } 871 } 872 873 // Since returns the time elapsed since t. 874 // It is shorthand for time.Now().Sub(t). 875 func Since(t Time) Duration { 876 var now Time 877 if t.wall&hasMonotonic != 0 { 878 // Common case optimization: if t has monotonic time, then Sub will use only it. 879 now = Time{hasMonotonic, runtimeNano() - startNano, nil} 880 } else { 881 now = Now() 882 } 883 return now.Sub(t) 884 } 885 886 // Until returns the duration until t. 887 // It is shorthand for t.Sub(time.Now()). 888 func Until(t Time) Duration { 889 var now Time 890 if t.wall&hasMonotonic != 0 { 891 // Common case optimization: if t has monotonic time, then Sub will use only it. 892 now = Time{hasMonotonic, runtimeNano() - startNano, nil} 893 } else { 894 now = Now() 895 } 896 return t.Sub(now) 897 } 898 899 // AddDate returns the time corresponding to adding the 900 // given number of years, months, and days to t. 901 // For example, AddDate(-1, 2, 3) applied to January 1, 2011 902 // returns March 4, 2010. 903 // 904 // AddDate normalizes its result in the same way that Date does, 905 // so, for example, adding one month to October 31 yields 906 // December 1, the normalized form for November 31. 907 func (t Time) AddDate(years int, months int, days int) Time { 908 year, month, day := t.Date() 909 hour, min, sec := t.Clock() 910 return Date(year+years, month+Month(months), day+days, hour, min, sec, int(t.nsec()), t.Location()) 911 } 912 913 const ( 914 secondsPerMinute = 60 915 secondsPerHour = 60 * secondsPerMinute 916 secondsPerDay = 24 * secondsPerHour 917 secondsPerWeek = 7 * secondsPerDay 918 daysPer400Years = 365*400 + 97 919 daysPer100Years = 365*100 + 24 920 daysPer4Years = 365*4 + 1 921 ) 922 923 // date computes the year, day of year, and when full=true, 924 // the month and day in which t occurs. 925 func (t Time) date(full bool) (year int, month Month, day int, yday int) { 926 return absDate(t.abs(), full) 927 } 928 929 // absDate is like date but operates on an absolute time. 930 func absDate(abs uint64, full bool) (year int, month Month, day int, yday int) { 931 // Split into time and day. 932 d := abs / secondsPerDay 933 934 // Account for 400 year cycles. 935 n := d / daysPer400Years 936 y := 400 * n 937 d -= daysPer400Years * n 938 939 // Cut off 100-year cycles. 940 // The last cycle has one extra leap year, so on the last day 941 // of that year, day / daysPer100Years will be 4 instead of 3. 942 // Cut it back down to 3 by subtracting n>>2. 943 n = d / daysPer100Years 944 n -= n >> 2 945 y += 100 * n 946 d -= daysPer100Years * n 947 948 // Cut off 4-year cycles. 949 // The last cycle has a missing leap year, which does not 950 // affect the computation. 951 n = d / daysPer4Years 952 y += 4 * n 953 d -= daysPer4Years * n 954 955 // Cut off years within a 4-year cycle. 956 // The last year is a leap year, so on the last day of that year, 957 // day / 365 will be 4 instead of 3. Cut it back down to 3 958 // by subtracting n>>2. 959 n = d / 365 960 n -= n >> 2 961 y += n 962 d -= 365 * n 963 964 year = int(int64(y) + absoluteZeroYear) 965 yday = int(d) 966 967 if !full { 968 return 969 } 970 971 day = yday 972 if isLeap(year) { 973 // Leap year 974 switch { 975 case day > 31+29-1: 976 // After leap day; pretend it wasn't there. 977 day-- 978 case day == 31+29-1: 979 // Leap day. 980 month = February 981 day = 29 982 return 983 } 984 } 985 986 // Estimate month on assumption that every month has 31 days. 987 // The estimate may be too low by at most one month, so adjust. 988 month = Month(day / 31) 989 end := int(daysBefore[month+1]) 990 var begin int 991 if day >= end { 992 month++ 993 begin = end 994 } else { 995 begin = int(daysBefore[month]) 996 } 997 998 month++ // because January is 1 999 day = day - begin + 1 1000 return 1001 } 1002 1003 // daysBefore[m] counts the number of days in a non-leap year 1004 // before month m begins. There is an entry for m=12, counting 1005 // the number of days before January of next year (365). 1006 var daysBefore = [...]int32{ 1007 0, 1008 31, 1009 31 + 28, 1010 31 + 28 + 31, 1011 31 + 28 + 31 + 30, 1012 31 + 28 + 31 + 30 + 31, 1013 31 + 28 + 31 + 30 + 31 + 30, 1014 31 + 28 + 31 + 30 + 31 + 30 + 31, 1015 31 + 28 + 31 + 30 + 31 + 30 + 31 + 31, 1016 31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 30, 1017 31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 30 + 31, 1018 31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 30 + 31 + 30, 1019 31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 30 + 31 + 30 + 31, 1020 } 1021 1022 func daysIn(m Month, year int) int { 1023 if m == February && isLeap(year) { 1024 return 29 1025 } 1026 return int(daysBefore[m] - daysBefore[m-1]) 1027 } 1028 1029 // daysSinceEpoch takes a year and returns the number of days from 1030 // the absolute epoch to the start of that year. 1031 // This is basically (year - zeroYear) * 365, but accounting for leap days. 1032 func daysSinceEpoch(year int) uint64 { 1033 y := uint64(int64(year) - absoluteZeroYear) 1034 1035 // Add in days from 400-year cycles. 1036 n := y / 400 1037 y -= 400 * n 1038 d := daysPer400Years * n 1039 1040 // Add in 100-year cycles. 1041 n = y / 100 1042 y -= 100 * n 1043 d += daysPer100Years * n 1044 1045 // Add in 4-year cycles. 1046 n = y / 4 1047 y -= 4 * n 1048 d += daysPer4Years * n 1049 1050 // Add in non-leap years. 1051 n = y 1052 d += 365 * n 1053 1054 return d 1055 } 1056 1057 // Provided by package runtime. 1058 func now() (sec int64, nsec int32, mono int64) 1059 1060 // runtimeNano returns the current value of the runtime clock in nanoseconds. 1061 //go:linkname runtimeNano runtime.nanotime 1062 func runtimeNano() int64 1063 1064 // Monotonic times are reported as offsets from startNano. 1065 // We initialize startNano to runtimeNano() - 1 so that on systems where 1066 // monotonic time resolution is fairly low (e.g. Windows 2008 1067 // which appears to have a default resolution of 15ms), 1068 // we avoid ever reporting a monotonic time of 0. 1069 // (Callers may want to use 0 as "time not set".) 1070 var startNano int64 = runtimeNano() - 1 1071 1072 // Now returns the current local time. 1073 func Now() Time { 1074 sec, nsec, mono := now() 1075 mono -= startNano 1076 sec += unixToInternal - minWall 1077 if uint64(sec)>>33 != 0 { 1078 return Time{uint64(nsec), sec + minWall, Local} 1079 } 1080 return Time{hasMonotonic | uint64(sec)<<nsecShift | uint64(nsec), mono, Local} 1081 } 1082 1083 func unixTime(sec int64, nsec int32) Time { 1084 return Time{uint64(nsec), sec + unixToInternal, Local} 1085 } 1086 1087 // UTC returns t with the location set to UTC. 1088 func (t Time) UTC() Time { 1089 t.setLoc(&utcLoc) 1090 return t 1091 } 1092 1093 // Local returns t with the location set to local time. 1094 func (t Time) Local() Time { 1095 t.setLoc(Local) 1096 return t 1097 } 1098 1099 // In returns a copy of t representing the same time instant, but 1100 // with the copy's location information set to loc for display 1101 // purposes. 1102 // 1103 // In panics if loc is nil. 1104 func (t Time) In(loc *Location) Time { 1105 if loc == nil { 1106 panic("time: missing Location in call to Time.In") 1107 } 1108 t.setLoc(loc) 1109 return t 1110 } 1111 1112 // Location returns the time zone information associated with t. 1113 func (t Time) Location() *Location { 1114 l := t.loc 1115 if l == nil { 1116 l = UTC 1117 } 1118 return l 1119 } 1120 1121 // Zone computes the time zone in effect at time t, returning the abbreviated 1122 // name of the zone (such as "CET") and its offset in seconds east of UTC. 1123 func (t Time) Zone() (name string, offset int) { 1124 name, offset, _, _, _ = t.loc.lookup(t.unixSec()) 1125 return 1126 } 1127 1128 // Unix returns t as a Unix time, the number of seconds elapsed 1129 // since January 1, 1970 UTC. The result does not depend on the 1130 // location associated with t. 1131 // Unix-like operating systems often record time as a 32-bit 1132 // count of seconds, but since the method here returns a 64-bit 1133 // value it is valid for billions of years into the past or future. 1134 func (t Time) Unix() int64 { 1135 return t.unixSec() 1136 } 1137 1138 // UnixMilli returns t as a Unix time, the number of milliseconds elapsed since 1139 // January 1, 1970 UTC. The result is undefined if the Unix time in 1140 // milliseconds cannot be represented by an int64 (a date more than 292 million 1141 // years before or after 1970). The result does not depend on the 1142 // location associated with t. 1143 func (t Time) UnixMilli() int64 { 1144 return t.unixSec()*1e3 + int64(t.nsec())/1e6 1145 } 1146 1147 // UnixMicro returns t as a Unix time, the number of microseconds elapsed since 1148 // January 1, 1970 UTC. The result is undefined if the Unix time in 1149 // microseconds cannot be represented by an int64 (a date before year -290307 or 1150 // after year 294246). The result does not depend on the location associated 1151 // with t. 1152 func (t Time) UnixMicro() int64 { 1153 return t.unixSec()*1e6 + int64(t.nsec())/1e3 1154 } 1155 1156 // UnixNano returns t as a Unix time, the number of nanoseconds elapsed 1157 // since January 1, 1970 UTC. The result is undefined if the Unix time 1158 // in nanoseconds cannot be represented by an int64 (a date before the year 1159 // 1678 or after 2262). Note that this means the result of calling UnixNano 1160 // on the zero Time is undefined. The result does not depend on the 1161 // location associated with t. 1162 func (t Time) UnixNano() int64 { 1163 return (t.unixSec())*1e9 + int64(t.nsec()) 1164 } 1165 1166 const timeBinaryVersion byte = 1 1167 1168 // MarshalBinary implements the encoding.BinaryMarshaler interface. 1169 func (t Time) MarshalBinary() ([]byte, error) { 1170 var offsetMin int16 // minutes east of UTC. -1 is UTC. 1171 1172 if t.Location() == UTC { 1173 offsetMin = -1 1174 } else { 1175 _, offset := t.Zone() 1176 if offset%60 != 0 { 1177 return nil, errors.New("Time.MarshalBinary: zone offset has fractional minute") 1178 } 1179 offset /= 60 1180 if offset < -32768 || offset == -1 || offset > 32767 { 1181 return nil, errors.New("Time.MarshalBinary: unexpected zone offset") 1182 } 1183 offsetMin = int16(offset) 1184 } 1185 1186 sec := t.sec() 1187 nsec := t.nsec() 1188 enc := []byte{ 1189 timeBinaryVersion, // byte 0 : version 1190 byte(sec >> 56), // bytes 1-8: seconds 1191 byte(sec >> 48), 1192 byte(sec >> 40), 1193 byte(sec >> 32), 1194 byte(sec >> 24), 1195 byte(sec >> 16), 1196 byte(sec >> 8), 1197 byte(sec), 1198 byte(nsec >> 24), // bytes 9-12: nanoseconds 1199 byte(nsec >> 16), 1200 byte(nsec >> 8), 1201 byte(nsec), 1202 byte(offsetMin >> 8), // bytes 13-14: zone offset in minutes 1203 byte(offsetMin), 1204 } 1205 1206 return enc, nil 1207 } 1208 1209 // UnmarshalBinary implements the encoding.BinaryUnmarshaler interface. 1210 func (t *Time) UnmarshalBinary(data []byte) error { 1211 buf := data 1212 if len(buf) == 0 { 1213 return errors.New("Time.UnmarshalBinary: no data") 1214 } 1215 1216 if buf[0] != timeBinaryVersion { 1217 return errors.New("Time.UnmarshalBinary: unsupported version") 1218 } 1219 1220 if len(buf) != /*version*/ 1+ /*sec*/ 8+ /*nsec*/ 4+ /*zone offset*/ 2 { 1221 return errors.New("Time.UnmarshalBinary: invalid length") 1222 } 1223 1224 buf = buf[1:] 1225 sec := int64(buf[7]) | int64(buf[6])<<8 | int64(buf[5])<<16 | int64(buf[4])<<24 | 1226 int64(buf[3])<<32 | int64(buf[2])<<40 | int64(buf[1])<<48 | int64(buf[0])<<56 1227 1228 buf = buf[8:] 1229 nsec := int32(buf[3]) | int32(buf[2])<<8 | int32(buf[1])<<16 | int32(buf[0])<<24 1230 1231 buf = buf[4:] 1232 offset := int(int16(buf[1])|int16(buf[0])<<8) * 60 1233 1234 *t = Time{} 1235 t.wall = uint64(nsec) 1236 t.ext = sec 1237 1238 if offset == -1*60 { 1239 t.setLoc(&utcLoc) 1240 } else if _, localoff, _, _, _ := Local.lookup(t.unixSec()); offset == localoff { 1241 t.setLoc(Local) 1242 } else { 1243 t.setLoc(FixedZone("", offset)) 1244 } 1245 1246 return nil 1247 } 1248 1249 // TODO(rsc): Remove GobEncoder, GobDecoder, MarshalJSON, UnmarshalJSON in Go 2. 1250 // The same semantics will be provided by the generic MarshalBinary, MarshalText, 1251 // UnmarshalBinary, UnmarshalText. 1252 1253 // GobEncode implements the gob.GobEncoder interface. 1254 func (t Time) GobEncode() ([]byte, error) { 1255 return t.MarshalBinary() 1256 } 1257 1258 // GobDecode implements the gob.GobDecoder interface. 1259 func (t *Time) GobDecode(data []byte) error { 1260 return t.UnmarshalBinary(data) 1261 } 1262 1263 // MarshalJSON implements the json.Marshaler interface. 1264 // The time is a quoted string in RFC 3339 format, with sub-second precision added if present. 1265 func (t Time) MarshalJSON() ([]byte, error) { 1266 if y := t.Year(); y < 0 || y >= 10000 { 1267 // RFC 3339 is clear that years are 4 digits exactly. 1268 // See golang.org/issue/4556#c15 for more discussion. 1269 return nil, errors.New("Time.MarshalJSON: year outside of range [0,9999]") 1270 } 1271 1272 b := make([]byte, 0, len(RFC3339Nano)+2) 1273 b = append(b, '"') 1274 b = t.AppendFormat(b, RFC3339Nano) 1275 b = append(b, '"') 1276 return b, nil 1277 } 1278 1279 // UnmarshalJSON implements the json.Unmarshaler interface. 1280 // The time is expected to be a quoted string in RFC 3339 format. 1281 func (t *Time) UnmarshalJSON(data []byte) error { 1282 // Ignore null, like in the main JSON package. 1283 if string(data) == "null" { 1284 return nil 1285 } 1286 // Fractional seconds are handled implicitly by Parse. 1287 var err error 1288 *t, err = Parse(`"`+RFC3339+`"`, string(data)) 1289 return err 1290 } 1291 1292 // MarshalText implements the encoding.TextMarshaler interface. 1293 // The time is formatted in RFC 3339 format, with sub-second precision added if present. 1294 func (t Time) MarshalText() ([]byte, error) { 1295 if y := t.Year(); y < 0 || y >= 10000 { 1296 return nil, errors.New("Time.MarshalText: year outside of range [0,9999]") 1297 } 1298 1299 b := make([]byte, 0, len(RFC3339Nano)) 1300 return t.AppendFormat(b, RFC3339Nano), nil 1301 } 1302 1303 // UnmarshalText implements the encoding.TextUnmarshaler interface. 1304 // The time is expected to be in RFC 3339 format. 1305 func (t *Time) UnmarshalText(data []byte) error { 1306 // Fractional seconds are handled implicitly by Parse. 1307 var err error 1308 *t, err = Parse(RFC3339, string(data)) 1309 return err 1310 } 1311 1312 // Unix returns the local Time corresponding to the given Unix time, 1313 // sec seconds and nsec nanoseconds since January 1, 1970 UTC. 1314 // It is valid to pass nsec outside the range [0, 999999999]. 1315 // Not all sec values have a corresponding time value. One such 1316 // value is 1<<63-1 (the largest int64 value). 1317 func Unix(sec int64, nsec int64) Time { 1318 if nsec < 0 || nsec >= 1e9 { 1319 n := nsec / 1e9 1320 sec += n 1321 nsec -= n * 1e9 1322 if nsec < 0 { 1323 nsec += 1e9 1324 sec-- 1325 } 1326 } 1327 return unixTime(sec, int32(nsec)) 1328 } 1329 1330 // UnixMilli returns the local Time corresponding to the given Unix time, 1331 // msec milliseconds since January 1, 1970 UTC. 1332 func UnixMilli(msec int64) Time { 1333 return Unix(msec/1e3, (msec%1e3)*1e6) 1334 } 1335 1336 // UnixMicro returns the local Time corresponding to the given Unix time, 1337 // usec microseconds since January 1, 1970 UTC. 1338 func UnixMicro(usec int64) Time { 1339 return Unix(usec/1e6, (usec%1e6)*1e3) 1340 } 1341 1342 // IsDST reports whether the time in the configured location is in Daylight Savings Time. 1343 func (t Time) IsDST() bool { 1344 _, _, _, _, isDST := t.loc.lookup(t.Unix()) 1345 return isDST 1346 } 1347 1348 func isLeap(year int) bool { 1349 return year%4 == 0 && (year%100 != 0 || year%400 == 0) 1350 } 1351 1352 // norm returns nhi, nlo such that 1353 // hi * base + lo == nhi * base + nlo 1354 // 0 <= nlo < base 1355 func norm(hi, lo, base int) (nhi, nlo int) { 1356 if lo < 0 { 1357 n := (-lo-1)/base + 1 1358 hi -= n 1359 lo += n * base 1360 } 1361 if lo >= base { 1362 n := lo / base 1363 hi += n 1364 lo -= n * base 1365 } 1366 return hi, lo 1367 } 1368 1369 // Date returns the Time corresponding to 1370 // yyyy-mm-dd hh:mm:ss + nsec nanoseconds 1371 // in the appropriate zone for that time in the given location. 1372 // 1373 // The month, day, hour, min, sec, and nsec values may be outside 1374 // their usual ranges and will be normalized during the conversion. 1375 // For example, October 32 converts to November 1. 1376 // 1377 // A daylight savings time transition skips or repeats times. 1378 // For example, in the United States, March 13, 2011 2:15am never occurred, 1379 // while November 6, 2011 1:15am occurred twice. In such cases, the 1380 // choice of time zone, and therefore the time, is not well-defined. 1381 // Date returns a time that is correct in one of the two zones involved 1382 // in the transition, but it does not guarantee which. 1383 // 1384 // Date panics if loc is nil. 1385 func Date(year int, month Month, day, hour, min, sec, nsec int, loc *Location) Time { 1386 if loc == nil { 1387 panic("time: missing Location in call to Date") 1388 } 1389 1390 // Normalize month, overflowing into year. 1391 m := int(month) - 1 1392 year, m = norm(year, m, 12) 1393 month = Month(m) + 1 1394 1395 // Normalize nsec, sec, min, hour, overflowing into day. 1396 sec, nsec = norm(sec, nsec, 1e9) 1397 min, sec = norm(min, sec, 60) 1398 hour, min = norm(hour, min, 60) 1399 day, hour = norm(day, hour, 24) 1400 1401 // Compute days since the absolute epoch. 1402 d := daysSinceEpoch(year) 1403 1404 // Add in days before this month. 1405 d += uint64(daysBefore[month-1]) 1406 if isLeap(year) && month >= March { 1407 d++ // February 29 1408 } 1409 1410 // Add in days before today. 1411 d += uint64(day - 1) 1412 1413 // Add in time elapsed today. 1414 abs := d * secondsPerDay 1415 abs += uint64(hour*secondsPerHour + min*secondsPerMinute + sec) 1416 1417 unix := int64(abs) + (absoluteToInternal + internalToUnix) 1418 1419 // Look for zone offset for expected time, so we can adjust to UTC. 1420 // The lookup function expects UTC, so first we pass unix in the 1421 // hope that it will not be too close to a zone transition, 1422 // and then adjust if it is. 1423 _, offset, start, end, _ := loc.lookup(unix) 1424 if offset != 0 { 1425 utc := unix - int64(offset) 1426 // If utc is valid for the time zone we found, then we have the right offset. 1427 // If not, we get the correct offset by looking up utc in the location. 1428 if utc < start || utc >= end { 1429 _, offset, _, _, _ = loc.lookup(utc) 1430 } 1431 unix -= int64(offset) 1432 } 1433 1434 t := unixTime(unix, int32(nsec)) 1435 t.setLoc(loc) 1436 return t 1437 } 1438 1439 // Truncate returns the result of rounding t down to a multiple of d (since the zero time). 1440 // If d <= 0, Truncate returns t stripped of any monotonic clock reading but otherwise unchanged. 1441 // 1442 // Truncate operates on the time as an absolute duration since the 1443 // zero time; it does not operate on the presentation form of the 1444 // time. Thus, Truncate(Hour) may return a time with a non-zero 1445 // minute, depending on the time's Location. 1446 func (t Time) Truncate(d Duration) Time { 1447 t.stripMono() 1448 if d <= 0 { 1449 return t 1450 } 1451 _, r := div(t, d) 1452 return t.Add(-r) 1453 } 1454 1455 // Round returns the result of rounding t to the nearest multiple of d (since the zero time). 1456 // The rounding behavior for halfway values is to round up. 1457 // If d <= 0, Round returns t stripped of any monotonic clock reading but otherwise unchanged. 1458 // 1459 // Round operates on the time as an absolute duration since the 1460 // zero time; it does not operate on the presentation form of the 1461 // time. Thus, Round(Hour) may return a time with a non-zero 1462 // minute, depending on the time's Location. 1463 func (t Time) Round(d Duration) Time { 1464 t.stripMono() 1465 if d <= 0 { 1466 return t 1467 } 1468 _, r := div(t, d) 1469 if lessThanHalf(r, d) { 1470 return t.Add(-r) 1471 } 1472 return t.Add(d - r) 1473 } 1474 1475 // div divides t by d and returns the quotient parity and remainder. 1476 // We don't use the quotient parity anymore (round half up instead of round to even) 1477 // but it's still here in case we change our minds. 1478 func div(t Time, d Duration) (qmod2 int, r Duration) { 1479 neg := false 1480 nsec := t.nsec() 1481 sec := t.sec() 1482 if sec < 0 { 1483 // Operate on absolute value. 1484 neg = true 1485 sec = -sec 1486 nsec = -nsec 1487 if nsec < 0 { 1488 nsec += 1e9 1489 sec-- // sec >= 1 before the -- so safe 1490 } 1491 } 1492 1493 switch { 1494 // Special case: 2d divides 1 second. 1495 case d < Second && Second%(d+d) == 0: 1496 qmod2 = int(nsec/int32(d)) & 1 1497 r = Duration(nsec % int32(d)) 1498 1499 // Special case: d is a multiple of 1 second. 1500 case d%Second == 0: 1501 d1 := int64(d / Second) 1502 qmod2 = int(sec/d1) & 1 1503 r = Duration(sec%d1)*Second + Duration(nsec) 1504 1505 // General case. 1506 // This could be faster if more cleverness were applied, 1507 // but it's really only here to avoid special case restrictions in the API. 1508 // No one will care about these cases. 1509 default: 1510 // Compute nanoseconds as 128-bit number. 1511 sec := uint64(sec) 1512 tmp := (sec >> 32) * 1e9 1513 u1 := tmp >> 32 1514 u0 := tmp << 32 1515 tmp = (sec & 0xFFFFFFFF) * 1e9 1516 u0x, u0 := u0, u0+tmp 1517 if u0 < u0x { 1518 u1++ 1519 } 1520 u0x, u0 = u0, u0+uint64(nsec) 1521 if u0 < u0x { 1522 u1++ 1523 } 1524 1525 // Compute remainder by subtracting r<<k for decreasing k. 1526 // Quotient parity is whether we subtract on last round. 1527 d1 := uint64(d) 1528 for d1>>63 != 1 { 1529 d1 <<= 1 1530 } 1531 d0 := uint64(0) 1532 for { 1533 qmod2 = 0 1534 if u1 > d1 || u1 == d1 && u0 >= d0 { 1535 // subtract 1536 qmod2 = 1 1537 u0x, u0 = u0, u0-d0 1538 if u0 > u0x { 1539 u1-- 1540 } 1541 u1 -= d1 1542 } 1543 if d1 == 0 && d0 == uint64(d) { 1544 break 1545 } 1546 d0 >>= 1 1547 d0 |= (d1 & 1) << 63 1548 d1 >>= 1 1549 } 1550 r = Duration(u0) 1551 } 1552 1553 if neg && r != 0 { 1554 // If input was negative and not an exact multiple of d, we computed q, r such that 1555 // q*d + r = -t 1556 // But the right answers are given by -(q-1), d-r: 1557 // q*d + r = -t 1558 // -q*d - r = t 1559 // -(q-1)*d + (d - r) = t 1560 qmod2 ^= 1 1561 r = d - r 1562 } 1563 return 1564 } 1565