gregorian to julian and back in go

gistfile1.go

package main

import (
	"fmt"
	"time"
)

func main() {
	today := time.Now()
	julian := GregorianToJulian(today.Year(), int(today.Month()), today.Day())

	fmt.Println(julian)

	year, month, day := JulianToGregorian(julian)

	fmt.Println(time.Date(year, time.Month(month), day, 0, 0, 0, 0, time.Local))
	fmt.Println(time.Now())
}

func GregorianToJulian(y, m, d int) int {
	return 367*y - 7*(y+(m+9)/12)/4 - 3*((y+(m-9)/7)/100+1)/4 + (275*m)/9 + d + 1721029
}

func JulianToGregorian(jd int) (year, month, day 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 y, m, d
}

Well that sucks.

Run on 2023-11-26:

2455146
2009-11-10 00:00:00 +0000 UTC
2009-11-10 23:00:00 +0000 UTC m=+0.000000001