Fast conversion from date to Unix Timestamp

to_unix.go

func toUnix(year, month, day, hour, min, sec int) int64 {
	if month < 1 || month > 12 {
		return -1
	}

	leap := 0
	if (year%4 == 0 && (year%100 != 0 || year%400 == 0)) && month >= 3 {
		leap = 1 // February 29
	}

	return int64((365*year - 719528 + day - 1 + (year+3)/4 - (year+99)/100 + (year+399)/400 + int([]int{0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334}[month-1]) + leap) * 86400 + hour * 3600 + min * 60 + sec)
}