Date Format Change

I have a form in my web page that everyone enters in a date and clicks submit. On the click of submit button the date is sent to the sql server and runs a stored procedure. My problem is that everyone enters the date in a dd/mm/yy format. The sql server needs the date to be entered in a yyyy/mm/dd for the stored procedure to run.

Is there any code which I can run in order to change the date format around (FROM dd/mm/yy -- TO -- yyyy/mm/dd) on the onclick event of the submit button on my form.
The html code for my form is as follows
<form action="" method="post" name="accounting" id="accounting">
<input name="date" type="text" id="date">
<input type="submit" name="Submit" value="Submit">
</form>

I would really appreciate any help anyone can give to me as I am very new to any type of coding and find it difficult doing some of the simple things.
Thanks
Not even sure if asp is needed to do this. All I know is the page is as asp.

Dim myDate

// This is a really simple way, but one that wouldn't work for 19xx dates
myDate = "20" & request("date")

// More elegant would be:
myDate = FormatDate("%Y/%m/%d", request("date"))
// For that to work ASP would have to accept your inputted date as a date though.