function DateTime_DaysBetween(date1, date2) {
    var ONE_DAY = 1000 * 60 * 60 * 24
    var date1_ms = date1.getTime()
    var date2_ms = date2.getTime()

    return Math.round(Math.abs(date1_ms - date2_ms) / ONE_DAY)
}

function DateTime_DaysInMonth(iMonth, iYear) {
    return 32 - new Date(iYear, iMonth, 32).getDate();
}