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utils.go
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utils.go
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package calendar
import (
"time"
)
// Gregorian calendar start date
var LilianDate = time.Date(1582, 10, 15, 0, 0, 0, 0, time.UTC)
func YearRange(start, end int) []int {
var r []int
for i := start; i <= end; i++ {
r = append(r, i)
}
return r
}
func YearInRange(year int, yearRange []int) bool {
for _, y := range yearRange {
if y == year {
return true
}
}
return false
}
func IsWeekend(t time.Time) bool {
wd := t.Weekday()
return wd == time.Saturday || wd == time.Sunday
}
// Beginning Of Day is the first time of that day
func BOD(t time.Time) time.Time {
y, m, d := t.Date()
return time.Date(y, m, d, 0, 0, 0, 0, t.Location())
}
// End Of Day is the last time of that day
func EOD(t time.Time) time.Time {
y, m, d := t.Date()
return time.Date(y, m, d, 23, 59, 59, 999999999, t.Location())
}
// Nth occurrence of a weekday like 3rd monday
func NthWeekday(year int, month time.Month, weekday time.Weekday, n int, loc *time.Location) time.Time {
if n == 0 {
return time.Time{}
}
if n < 0 {
n++
}
t := time.Date(year, month, 1, 0, 0, 0, 0, loc)
wd := t.Weekday()
if weekday < wd {
return t.AddDate(0, 0, (7-int(wd-weekday))+((n-1)*7))
}
if weekday > wd {
return t.AddDate(0, 0, int(weekday-wd)+((n-1)*7))
}
return t.AddDate(0, 0, (n-1)*7)
}
// year -> day and month of Easter
func Easter(year int) (day int, month time.Month) {
// Meeus/Jones/Butcher algorithm
y := year
a := y % 19
b := y / 100
c := y % 100
d := b / 4
e := b % 4
f := (b + 8) / 25
g := (b - f + 1) / 3
h := (19*a + b - d - g + 15) % 30
i := c / 4
k := c % 4
l := (32 + 2*e + 2*i - h - k) % 7
m := (a + 11*h + 22*l) / 451
n := h + l - 7*m + 114
month = time.Month(n / 31)
day = (n % 31) + 1
return
}
// Gregorian calendar time -> Julian Day Number
func GtoJDN(t time.Time) int {
t = t.UTC()
a := (14 - int(t.Month())) / 12
y := t.Year() + 4800 - a
m := int(t.Month()) + 12*a - 3
return t.Day() + (153*m+2)/5 + 365*y + y/4 - y/100 + y/400 - 32045
}
// Julian calendar time -> Julian Day Number
func JtoJDN(t time.Time) int {
t = t.UTC()
a := (14 - int(t.Month())) / 12
y := t.Year() + 4800 - a
m := int(t.Month()) + 12*a - 3
return t.Day() + (153*m+2)/5 + 365*y + y/4 - 32083
}
// Hijri calendar time -> Julian Day Number
func HtoJDN(t time.Time) int {
t = t.UTC()
y := (10631*t.Year() - 10617) / 30
m := (325*int(t.Month()) - 320) / 11
d := t.Day()
return y + m + d + 1948439
}
// Julian Day Number -> Gregorian calendar time (UTC default loc if not provided)
func JDNtoG(jd int, loc ...*time.Location) time.Time {
a := jd + 32044
b := (4*a + 3) / 146097
c := a - 146097*b/4
d := (4*c + 3) / 1461
e := c - (1461*d)/4
m := (5*e + 2) / 153
day := e - (153*m+2)/5 + 1
month := time.Month(m + 3 - 12*(m/10))
year := 100*b + d - 4800 + m/10
t := time.Date(year, month, day, 12, 0, 0, 0, time.UTC)
if len(loc) != 0 {
t = t.In(loc[0])
}
return t
}
// Julian Day Number -> Julian calendar time (UTC default loc if not provided)
func JDNtoJ(jd int, loc ...*time.Location) time.Time {
b := 0
c := jd + 32082
d := (4*c + 3) / 1461
e := c - (1461*d)/4
m := (5*e + 2) / 153
day := e - (153*m+2)/5 + 1
month := time.Month(m + 3 - 12*(m/10))
year := 100*b + d - 4800 + m/10
t := time.Date(year, month, day, 12, 0, 0, 0, time.UTC)
if len(loc) != 0 {
t = t.In(loc[0])
}
return t
}
// Julian Day Number -> Hijri calendar time (UTC default loc if not provided)
func JDNtoH(jd int, loc ...*time.Location) time.Time {
k2 := 30*(jd-1948440) + 15
k1 := 11*((k2%10631)/30) + 5
year := k2/10631 + 1
month := time.Month(k1/325 + 1)
day := (k1%325)/11 + 1
t := time.Date(year, month, day, 12, 0, 0, 0, time.UTC)
if len(loc) != 0 {
t = t.In(loc[0])
}
return t
}
// Julian calendar Time -> Gregorian calendar Time
func JulianToGegorian(t time.Time) time.Time {
g := JDNtoG(JtoJDN(t), t.Location())
g = time.Date(g.Year(), g.Month(), g.Day(), t.Hour(), t.Minute(), t.Second(), t.Nanosecond(), g.Location())
return g
}
// Gregorian calendar Time -> Julian calendar Time
func GregorianToJulian(t time.Time) time.Time {
j := JDNtoJ(GtoJDN(t), t.Location())
j = time.Date(j.Year(), j.Month(), j.Day(), t.Hour(), t.Minute(), t.Second(), t.Nanosecond(), j.Location())
return j
}
// Hijri calendar Time -> Gregorian calendar Time
func HijriToGregorian(t time.Time) time.Time {
g := JDNtoG(HtoJDN(t), t.Location())
g = time.Date(g.Year(), g.Month(), g.Day(), t.Hour(), t.Minute(), t.Second(), t.Nanosecond(), g.Location())
return g
}
// Gregorian calendar Time -> Hijri calendar Time
func GregorianToHijri(t time.Time) time.Time {
j := JDNtoH(GtoJDN(t), t.Location())
j = time.Date(j.Year(), j.Month(), j.Day(), t.Hour(), t.Minute(), t.Second(), t.Nanosecond(), j.Location())
return j
}
// Gregorian Year -> Hijri Year
func HijriYear(gy int) int {
return int((float64(gy) - 621.5709) * 1.0306888)
}
// Is a Leap Year in the Julian calendar
func IsJulianLeapYear(year int) bool {
return year%4 == 0
}
// Is a Leap Year in the Gregorian calendar
func IsLeapYear(year int) bool {
return year%4 == 0 && year%100 != 0 || year%400 == 0
}
// Year, Month -> number of days in the month
func GetMonthDays(year int, month time.Month) int {
monthDays := map[time.Month]int{1: 31, 2: 28, 3: 31, 4: 30, 5: 31, 6: 30, 7: 31, 8: 31, 9: 30, 10: 31, 11: 30, 12: 31}
if month == time.February && IsLeapYear(year) {
return 29
}
return monthDays[month]
}
// Get the number of days in the Gregorian calendar year
func GetYearDays(year int) int {
if IsLeapYear(year) {
return 366
}
return 365
}
// Hijri Calendar months
const (
AlMuharram = time.Month(1)
Safar = time.Month(2)
RabiAlAwwal = time.Month(3)
RabiAlAkhir = time.Month(4)
JumadaAlUla = time.Month(5)
JumadaAlThaniyah = time.Month(6)
Rajab = time.Month(7)
ShaBan = time.Month(8)
Ramadan = time.Month(9)
Shawwal = time.Month(10)
DhuAlQaDah = time.Month(11)
DhuAlHijjah = time.Month(12)
)