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excelTime.go
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excelTime.go
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package xlsx_reader
import (
"math"
"time"
)
//儒略日期转换到格林尼治时间
func julianDateToGregorianTime(part1, part2 float64) time.Time {
part1I, part1F := math.Modf(part1)
part2I, part2F := math.Modf(part2)
julianDays := part1I + part2I
julianFraction := part1F + part2F
julianDays, julianFraction = shiftJulianToNoon(julianDays, julianFraction)
day, month, year := doTheFliegelAndVanFlandernAlgorithm(int(julianDays))
hours, minutes, seconds, nanoseconds := fractionOfADay(julianFraction)
return time.Date(year, time.Month(month), day, hours, minutes, seconds, nanoseconds, time.UTC)
}
func shiftJulianToNoon(julianDays, julianFraction float64) (float64, float64) {
switch {
case -0.5 < julianFraction && julianFraction < 0.5:
julianFraction += 0.5
case julianFraction >= 0.5:
julianDays++
julianFraction -= 0.5
case julianFraction <= -0.5:
julianDays--
julianFraction += 1.5
}
return julianDays, julianFraction
}
func doTheFliegelAndVanFlandernAlgorithm(jd int) (day, month, year int) {
l := jd + 68569
n := (4 * l) / 146097
l = l - (146097*n+3)/4
i := (4000 * (l + 1)) / 1461001
l = l - (1461*i)/4 + 31
j := (80 * l) / 2447
d := l - (2447*j)/80
l = j / 11
m := j + 2 - (12 * l)
y := 100*(n-49) + i + l
return d, m, y
}
func fractionOfADay(fraction float64) (hours, minutes, seconds, nanoseconds int) {
const (
c1us = 1e3
c1s = 1e9
c1day = 24 * 60 * 60 * c1s
)
frac := int64(c1day*fraction + c1us/2)
nanoseconds = int((frac%c1s)/c1us) * c1us
frac /= c1s
seconds = int(frac % 60)
frac /= 60
minutes = int(frac % 60)
hours = int(frac / 60)
return
}
//Excel float类型日期时间转换的 time类型
func GetExcelTime(excelTime float64, date1904 bool) time.Time {
const MDD int64 = 106750 // Max time.Duration Days, aprox. 290 years
var date time.Time
var intPart = int64(excelTime)
// Excel uses Julian dates prior to March 1st 1900, and Gregorian
// thereafter.
if intPart <= 61 {
const OFFSET1900 = 15018.0
const OFFSET1904 = 16480.0
const MJD0 float64 = 2400000.5
var date time.Time
if date1904 {
date = julianDateToGregorianTime(MJD0, excelTime+OFFSET1904)
} else {
date = julianDateToGregorianTime(MJD0, excelTime+OFFSET1900)
}
return date
}
var floatPart = excelTime - float64(intPart)
var dayNanoSeconds float64 = 24 * 60 * 60 * 1000 * 1000 * 1000
if date1904 {
date = time.Date(1904, 1, 1, 0, 0, 0, 0, time.UTC)
} else {
date = time.Date(1899, 12, 30, 0, 0, 0, 0, time.UTC)
}
// Duration is limited to aprox. 290 years
for intPart > MDD {
durationDays := time.Duration(MDD) * time.Hour * 24
date = date.Add(durationDays)
intPart = intPart - MDD
}
durationDays := time.Duration(intPart) * time.Hour * 24
durationPart := time.Duration(dayNanoSeconds * floatPart)
return date.Add(durationDays).Add(durationPart)
}