I'm trying to store a value from a birthday field in a custom database table using mapping with a date datatype. I have used similar code below using the calendar option and it works perfectly. However, the Birthday field keeps adding the date as 12-31-1969 (i.e. invalid date format). This is the script that I put into the Script called on form process section and then map the hidden, FormattedBirthday field to the DB. Any idea what I am doing wrong?

$_POST = date('Y-m-d H:i:s', strtotime($_POST));