Is it illegal for a 25 year old to date a 17 year old in the state of Maryland?

There are no laws for dating in the US, just regarding sex which you can see below. The minor will need parents consent for dating of course as always.

The age of consent in Maryland is 16. An exception is made when the actor is not at least four years older than the victim. However, if someone in a "position of authority" engages in a sexual act with a minor, he or she may be guilty of sexual offense in the fourth degree as specified by Maryland Code § 3-308.