Since you stated this is homework in Date pattern matching and that you are not allowed external modules (not reinventing good modules is the correct way) - I am only going to give a nudge in the right direction.

Don't use a regex, use split, as how to do that I am going to leave that up to you. That should get you what you want most of the time

grep

Mynd you, mønk bites Kan be pretti nasti...