115 lines
3.1 KiB
Go
115 lines
3.1 KiB
Go
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package internal
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import (
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"errors"
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"math"
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"time"
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)
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// ErrInvalidCivilDate 日期非法 / invalid civil date.
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var ErrInvalidCivilDate = errors.New("invalid civil date")
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// Date2JD 日期转儒略日 / Julian day from a civil time.
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func Date2JD(date time.Time) float64 {
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day := float64(date.Day()) + float64(date.Hour())/24.0 + float64(date.Minute())/1440.0 + float64(date.Second())/86400.0 + float64(date.Nanosecond())/86400000000000.0
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return JDCalc(date.Year(), int(date.Month()), day)
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}
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// JDCalc 由公历年月日计算儒略日 / Julian day from a civil date.
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func JDCalc(year, month int, day float64) float64 {
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if !validCivilDate(year, month, day) {
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return math.NaN()
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}
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effectiveYear, effectiveMonth, effectiveDay := year, month, int(math.Floor(day))
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if month == 1 || month == 2 {
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year--
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month += 12
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}
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correction := 0
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if effectiveYear > 1582 || (effectiveYear == 1582 && (effectiveMonth > 10 || (effectiveMonth == 10 && effectiveDay >= 15))) {
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century := int(year / 100)
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correction = 2 - century + int(century/4)
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}
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return math.Floor(365.25*(float64(year)+4716.0)) + math.Floor(30.6001*float64(month+1)) + day + float64(correction) - 1524.5
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}
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func validCivilDate(year, month int, day float64) bool {
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if math.IsNaN(day) || math.IsInf(day, 0) || month < 1 || month > 12 || day < 1 {
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return false
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}
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dayInt := int(math.Floor(day))
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if dayInt > daysInCivilMonth(year, month) {
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return false
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}
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return !(year == 1582 && month == 10 && day >= 5 && day < 15)
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}
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func daysInCivilMonth(year, month int) int {
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switch month {
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case 1, 3, 5, 7, 8, 10, 12:
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return 31
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case 4, 6, 9, 11:
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return 30
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case 2:
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if isCivilLeapYear(year, month, 1) {
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return 29
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}
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return 28
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default:
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return 0
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}
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}
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func isCivilLeapYear(year, month int, day float64) bool {
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if year < 1582 || (year == 1582 && (month < 10 || (month == 10 && day <= 4))) {
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return year%4 == 0
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}
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if year%400 == 0 {
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return true
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}
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if year%100 == 0 {
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return false
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}
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return year%4 == 0
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}
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// JD2DateByZone 儒略日转目标时区日期 / convert a Julian day to a target timezone.
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func JD2DateByZone(jd float64, tz *time.Location, byZone bool) time.Time {
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jd += 0.5
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z := float64(int(jd))
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fraction := jd - z
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a := z
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if z >= 2299161.0 {
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alpha := math.Floor((z - 1867216.25) / 36524.25)
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a = z + 1 + alpha - math.Floor(alpha/4)
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}
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b := a + 1524
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c := math.Floor((b - 122.1) / 365.25)
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d := math.Floor(365.25 * c)
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e := math.Floor((b - d) / 30.6001)
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days := b - d - math.Floor(30.6001*e) + fraction
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month := e - 1
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if e >= 14 {
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month = e - 13
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}
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year := c - 4716
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if month <= 2 {
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year = c - 4715
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}
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seconds := (days - math.Floor(days)) * 86400
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day := math.Floor(days)
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date := time.Date(int(year), time.Month(int(month)), int(day), 0, 0, 0, 0, time.UTC).
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Add(time.Duration(int64(1000000000 * seconds)))
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if !byZone {
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return date.In(tz)
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}
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y, m, dayInt := date.Date()
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h, minute, second := date.Clock()
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return time.Date(y, m, dayInt, h, minute, second, date.Nanosecond(), tz)
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}
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// UTC2UT1 轻量民用时转世界时，忽略 DUT1（|UT1−UTC| < 0.9 s） / lightweight UTC to UT1, DUT1 ignored.
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func UTC2UT1(jd float64) float64 {
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return jd
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}
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