65 lines
1.8 KiB
Go
65 lines
1.8 KiB
Go
|
/*
|
||
|
|
Copyright 2017 SAP SE
|
||
|
|
|
||
|
|
Licensed under the Apache License, Version 2.0 (the "License");
|
||
|
|
you may not use this file except in compliance with the License.
|
||
|
|
You may obtain a copy of the License at
|
||
|
|
|
||
|
|
http://www.apache.org/licenses/LICENSE-2.0
|
||
|
|
|
||
|
|
Unless required by applicable law or agreed to in writing, software
|
||
|
|
distributed under the License is distributed on an "AS IS" BASIS,
|
||
|
|
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
||
|
|
See the License for the specific language governing permissions and
|
||
|
|
limitations under the License.
|
||
|
|
*/
|
||
|
|
|
||
|
|
package protocol
|
||
|
|
|
||
|
|
import (
|
||
|
|
"time"
|
||
|
|
)
|
||
|
|
|
||
|
|
const gregorianDay = 2299161 // Start date of Gregorian Calendar as Julian Day Number
|
||
|
|
var gregorianDate = julianDayToTime(gregorianDay) // Start date of Gregorian Calendar (1582-10-15)
|
||
|
|
|
||
|
|
// timeToJulianDay returns the Julian Date Number of time's date components.
|
||
|
|
// The algorithm is taken from https://en.wikipedia.org/wiki/Julian_day.
|
||
|
|
func timeToJulianDay(t time.Time) int {
|
||
|
|
|
||
|
|
t = t.UTC()
|
||
|
|
|
||
|
|
month := int(t.Month())
|
||
|
|
|
||
|
|
a := (14 - month) / 12
|
||
|
|
y := t.Year() + 4800 - a
|
||
|
|
m := month + (12 * a) - 3
|
||
|
|
|
||
|
|
if t.Before(gregorianDate) { // Julian Calendar
|
||
|
|
return t.Day() + (153*m+2)/5 + 365*y + y/4 - 32083
|
||
|
|
} else { // Gregorian Calendar
|
||
|
|
return t.Day() + (153*m+2)/5 + 365*y + y/4 - y/100 + y/400 - 32045
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
// JulianDayToTime returns the correcponding UTC date for a Julian Day Number.
|
||
|
|
// The algorithm is taken from https://en.wikipedia.org/wiki/Julian_day.
|
||
|
|
func julianDayToTime(jd int) time.Time {
|
||
|
|
var f int
|
||
|
|
|
||
|
|
if jd < gregorianDay {
|
||
|
|
f = jd + 1401
|
||
|
|
} else {
|
||
|
|
f = jd + 1401 + (((4*jd+274277)/146097)*3)/4 - 38
|
||
|
|
}
|
||
|
|
|
||
|
|
e := 4*f + 3
|
||
|
|
g := (e % 1461) / 4
|
||
|
|
h := 5*g + 2
|
||
|
|
day := (h%153)/5 + 1
|
||
|
|
month := (h/153+2)%12 + 1
|
||
|
|
year := (e / 1461) - 4716 + (12+2-month)/12
|
||
|
|
|
||
|
|
return time.Date(year, time.Month(month), day, 0, 0, 0, 0, time.UTC)
|
||
|
|
}
|