Babyswap expiration

[DopeyDame]

I know the babyswap passes now usually expire at the end of the month. But if it's already the last day or two of the month, do they expire that day, or do they roll over to the next month?

 

[Day-Day]

During our recent visit at the end of May, the passes we picked up on 31-May expired on that day. All of our passes we got on the days prior to 31-May also expired on 31-May.