I usually take it as assuming they expire at the beginning of the month, but I can't imagine it would make much difference either way! I do know you aren't supposed to use them more than a month or so past the expiration date, because my mom was a champ at keeping expired meds for years and insisting they were still good. I called a pharmacist on her once! LOL He said keeping them more than a month or so past the expiration date was useless.

Maybe one of our pharmacists here can weigh in?