Q548 How do I validate a start date and an end date so that start is less than end, and that end is before todays date, using the date format dd/mm/yyyy?

<script language="JavaScript"><!--
function padout(number) { return (number < 10) ? '0' + number : number; }

function y2k(number) { return (number < 1000) ? number + 1900 : number; }

function validate(what) {
    var startday = what.startday.options[what.startday.selectedIndex].value;
    var startmonth = what.startmonth.options[what.startmonth.selectedIndex].value;
    var startyear = what.startyear.options[what.startyear.selectedIndex].text;
    var endday = what.endday.options[what.endday.selectedIndex].value;
    var endmonth = what.endmonth.options[what.endmonth.selectedIndex].value;
    var endyear = what.endyear.options[what.endyear.selectedIndex].text;

    unvalidstartdate = startday + '/' + startmonth + '/' + startyear;
    unvalidenddate = endday + '/' + endmonth + '/' + endyear;

    var startdate = new Date(startyear-0,startmonth-1,startday-0);
    var enddate = new Date(endyear-0,endmonth-1,endday-0);

    var validstartdate = padout(startdate.getDate()) + '/' + padout(startdate.getMonth()+1) + '/' + y2k(startdate.getYear())
    var validenddate = padout(enddate.getDate()) + '/' + padout(enddate.getMonth()+1) + '/' + y2k(enddate.getYear())

    if (unvalidstartdate != validstartdate) {
        alert('Start Date: ' + what.startday.options[what.startday.selectedIndex].text +
                         ' ' + what.startmonth.options[what.startmonth.selectedIndex].text +
                         ' ' + what.startyear.options[what.startyear.selectedIndex].text + ' is invalid');
        return false;
    }

    if (unvalidenddate != validenddate) {
        alert('End Date: ' + what.endday.options[what.endday.selectedIndex].text +
                       ' ' + what.endmonth.options[what.endmonth.selectedIndex].text +
                       ' ' + what.endyear.options[what.endyear.selectedIndex].text + ' is invalid');
        return false;
    }

    starttime = Date.UTC(y2k(startdate.getYear()),startdate.getMonth(),startdate.getDate(),0,0,0);
    endtime = Date.UTC(y2k(enddate.getYear()),enddate.getMonth(),enddate.getDate(),0,0,0);

    if (starttime < endtime) {
        // valid
    }
    else {
        alert('Start Date is not less than End Date');
        return false
    }

    currentdate = new Date();
    currenttime = Date.UTC(y2k(currentdate.getYear()),currentdate.getMonth(),currentdate.getDate(),0,0,0);

    if (endtime < currenttime) {
        // valid
    }
    else {
        alert('End Date is not less than todays date');
        return false;
    }

    what.startdate.value = validstartdate;
    what.enddate.value = validenddate;
    return true;
}
//--></script>

<form>
Start Date:
<select name="startday">
<option value="01">1st
<option value="02">2nd
<option value="03">3rd
<option value="04">4th
<option value="05">5th
<option value="06">6th
<option value="07">7th
<option value="08">8th
<option value="09">9th
<option value="10">10th
<option value="11">11th
<option value="12">12th
<option value="13">13th
<option value="14">14th
<option value="15">15th
<option value="16">16th
<option value="17">17th
<option value="18">18th
<option value="19">19th
<option value="20">20th
<option value="21">21st
<option value="22">22nd
<option value="23">23rd
<option value="24">24th
<option value="25">25th
<option value="26">26th
<option value="27">27th
<option value="28">28th
<option value="29">29th
<option value="30">30th
<option value="31">31st
</select>

<select name="startmonth">
<option value="01">january
<option value="02">february
<option value="03">march
<option value="04">april
<option value="05">may
<option value="06">june
<option value="07">july
<option value="08">august
<option value="09">september
<option value="10">october
<option value="11">november
<option value="12">december
</select>

<select name="startyear">
<option>1990
<option>1991
<option>1992
<option>1993
<option>1994
<option>1995
<option>1996
<option>1997
<option>1998
<option>1999
<option>2000
<option>2001
<option>2002
<option>2003
<option>2004
<option>2005
<option>2006
<option>2007
<option>2008
<option>2009
</select>

<p>

End Date:
<select name="endday">
<option value="01">1st
<option value="02">2nd
<option value="03">3rd
<option value="04">4th
<option value="05">5th
<option value="06">6th
<option value="07">7th
<option value="08">8th
<option value="09">9th
<option value="10">10th
<option value="11">11th
<option value="12">12th
<option value="13">13th
<option value="14">14th
<option value="15">15th
<option value="16">16th
<option value="17">17th
<option value="18">18th
<option value="19">19th
<option value="20">20th
<option value="21">21st
<option value="22">22nd
<option value="23">23rd
<option value="24">24th
<option value="25">25th
<option value="26">26th
<option value="27">27th
<option value="28">28th
<option value="29">29th
<option value="30">30th
<option value="31">31st
</select>

<select name="endmonth">
<option value="01">january
<option value="02">february
<option value="03">march
<option value="04">april
<option value="05">may
<option value="06">june
<option value="07">july
<option value="08">august
<option value="09">september
<option value="10">october
<option value="11">november
<option value="12">december
</select>

<select name="endyear">
<option>1990
<option>1991
<option>1992
<option>1993
<option>1994
<option>1995
<option>1996
<option>1997
<option>1998
<option>1999
<option>2000
<option>2001
<option>2002
<option>2003
<option>2004
<option>2005
<option>2006
<option>2007
<option>2008
<option>2009
</select>

<input type="hidden" name="startdate">
<input type="hidden" name="enddate">

<p>

<input type="button" onClick="validate(this.form)" value="Validate">
</form>