I can see what Rennur is getting at.
Keeping it simple the timestamp attribute is one value consisting of a date part and a time part. In the db it's one field. So just because it's split on the screen for a user to enter the parts separately, it should not be considered entered/defined until both parts are completed.
Having said that, I can see though from supports point of view that this may be very difficult to achieve as a user may enter the date part, move to another field on the screen then move back to the time part?
I guess I'm not helping the discussion in that I can see both sides of the coin and don't have a practical answer in how to achieve it. In any event I'm now going back through my apps as I use split times everywhere and wasn't aware of this! So thanks Rennur for pointing it out.
Cheers Rod