For the date picker, please send a link so i can see the code in context.
The PHP Error means that in the php.ini file, there is no timezone set for the date.timezone
Edit the php.ini file and enter a vlid timezone for the date.timezone setting.
Alternatively, you can add the following at line 1 of the form page to set the time zone:
<?php
date_default_timezone_set('America/Chicago');
?>
The list of valid timezones is here...
http://www.php.net/manual/en/timezones.php