Problem with Regular Expression for Date

Hi,
I use a regular expression to validate the date.
But it does not work properly. See my code :
function checkdateformat(userinput){
var dateformat = /^d{1,2}(-|/|.)d{1,2}1d4}$/
return dateformat.test(userinput) //returns true or false depending on userinput
}
Is there any other regular expression available to check the date format.
Thanks.
