You can use the 'Creation date' wizard.
If you want to use a different way :
MySQL has an issue here :
stackoverflow.com/questions/168736/how-d...ysql-datetime-column
You can realize it with two methods.
1st Method (Triggers)
TODO in :
sql/install.mysql.utf8.sql
Add the SQL instructions at the installation (like triggers)
2nd Method
TODO in :
tables/[myTable].php
in the check() function :
Test the value and if the value is empty, fill it with the current time (PHP call)
mktime()
or
www.php.net/manual/fr/function.date.php#...unction.date-seealso
Hope it helps