If you want to keep track of this stuff then what SQL Hell suggests will only tell you when a record has been added to the database.
If you want to keep track of dates created and updated then have two fields:
DateCreated
LastUpdated
Do with DateCreated as SQL Hell says (with DateAdded - same thing)
With LastUpdate, put something like: Me.LastUpdated = Now() in the BeforeUpdate event of your form(s).