Date Validation by Javascript

I have two fields in a forom which are start date and end date, I want to check the end date cannot be early than the start date, I able to do it by using the code below but when I select single digit day and two digit day, it cannot compare, such as 5 and 20, even though 20 is later than 5 but it still prompt error.

Can javascript compare single digit and two digits or not?


function validateForm()
{
if (bookingform.endtime.value<=bookingform.starttime.value)
{
alert('Your End Hour must later than the start hour.')
bookingform.endtime.focus()
return false
}


if( (bookingform.rep_type[1].checked) || (bookingform.rep_type[2].checked) )
{
if((bookingform.rep_end_year.value==bookingform.ye ar.value) && (bookingform.rep_end_month.value==bookingform.mont h.value))
{
if(bookingform.rep_end_day.value<=bookingform.day.value)
{
alert("Your repeat end day must later than the start day")
bookingform.rep_end_day.focus()
return false
}
}

if ((bookingform.rep_end_year.value==bookingform.year .value) && (bookingform.rep_end_month.value<bookingform.month.value))
{
alert('Your Repeat End Month must later than the Start Month')
bookingform.rep_end_month.focus()
return false
}


if(bookingform.rep_end_year.value<bookingform.year.value)
{
if(bookingform.rep_end_month>bookingform.month.value)
{
alert("Your repeat end year must later than the start year")
bookingform.rep_end_year.focus()
return false
}
}


var aa=((bookingform.rep_end_year.value)-(bookingform.year.value));
if(aa>=2)
{
alert("Hello world")
return false
}
}
return true;
}

Why dont you try out writing your own function for converting your dates to timestamps.. It will be easy for comparison then.. Not a high end one.. Just a basic one

Somthing like

TmStamp=Day+Month+Year