If your spouse files a Complaint for Divorce against you, you have 30 days from the date you are served to file an Answer if served in the state of Maryland.   Maryland Rule 2-321(a).

You may also file a Counterclaim against your spouse.  Maryland Rule 2-331(a).

But if you file it more than 30 days after your Answer was due, your spouse can file a Motion to Strike your Counterclaim for being late.  The court shall grant the motion unless you can persuade the judge that the delay will not prejudice your spouse.  Maryland Rule 2-331(d).