[stomachmonkey]

You should have mobile deposited it on the spot.

As far as banks are concerned there is no thing as post dating a check.

It's a payment instrument that is supposed to be valid from the moment it is presented.

Banks won't look at it and say "oh, we have to wait X days to process this".

Not how any of that works.

If it bounced it costs both of you some money but you can always plead your case with your institution and if you are a valued customer they'll most likely waive it and he learns a lesson.