Useful date calculations for Javascript

Custom Date Functions for Javascript

Date.daysBetween01 = function( date1, date2 ) {
    //Get 1 day in milliseconds    var one_day=1000*60*60*24;

    // Convert both dates to milliseconds    var date1_ms = date1.getTime();
    var date2_ms = date2.getTime();

    // Calculate the difference in milliseconds    var difference_ms = date2_ms - date1_ms;

    // Convert back to days and return    return Math.round(difference_ms/one_day);
}