1) Object has autonumber
2) user creates record for object
3) entry form opens up and the user fills it out
4) a trigger is fired on save which turns the autonumber to a text, the trigger then changes the text of the auto number field to the text ([date] + ': ' + Owner.name)
5) the autonumber is turned back to an autonumber

1) user opens record and fills in a date field (which is the only thing I'm interested in)
2) The user has to fill in a name field which is unnecessary (for the user, in a mobile setting this is problematic or at least not elegant)
3)  User saves
4) name field is overwritten (date + ': ' + owner.name)

1) user opens record and fills out date (and does not have to fill out a name field)
2) user saves
3) trigger updates "key" field to (date + ': ' + owner.name)