the mysql database date column expects to receive the date formatted as yyyy-mm-dd. you will reformat the selections that where made to that format.
to do this:
1) make sure the value of the Year select list is a 4 digit year:
<option value="1990">1990</option>
2) make sure the value of the Month select list is the 2 digit month, not the month name:
<option value="01">January</option>
3) make sure the value of the day select list is the 2 digit day number:
<option value="01">1</option>
4) add a hidden form element to the page, but don't set a value for it.
5) add code to line 1 of the page to format the date, assuming the form element names are "year", "month", "day", "fullDate" (hidden element), the code to use would look like this:
<?php if($_SERVER['REQUEST_METHOD'] == "POST") $_POST["fullDate"] = date("Y-m-d", strtotime($_POST["year"]."/".$_POST["month"]."/".$_POST["day"])); ?>
6) in the insert record behavior, bind the date column to the fullDate hidden element which will contain the formatted date.
