On January 17, the Pennsylvania Supreme Court agreed to hear Baxter v Philadelphia Board of Elections, 395 EAL 2024. This is the case over the validity of the law that says postal ballots are invalid if the voter either forgets to include the date on the outer envelope, or puts an incorrect date. The lower court had invalidated the law on the basis of the State Constitution’s provision that elections shall be “free and equal.”
No other state invalidates postal ballots for that reason. Generally states don’t even ask for a date on the outer envelope.