If you had a dead-ball foul after time expired in the first (or third), period, what would you do?
No difference from the second (or 4th periods). Penalize the foul at the succeeding spot before the next play in the next period, if there is another period. That play will be the kickoff, if the next period is the 3rd period. If the next period is an extra period, the penalty is enforced at the 25 yard line on which the period will begin.
10-1-5 and 10-2-2-a (as Skybolt referenced).
Robert