September has 30 days. This is established. Calendars agree. Scientists agree. And yet, every year, products appear with a "best by" date of September 31, a day that has never occurred and will never occur.
We have compiled the definitive list of dates that do not exist:
- September 31. The most famous. Thirty days hath September, but someone didn't get the memo.
- February 30. Tried in Sweden in 1712. It did not stick.
- The 13th month. Smarch? No. Just no.
The question is not how these dates happen. The question is what happens to the food. If a juice carton says "best by sep 31," is it best forever? Is it never best? Our quality department looked into this and concluded that the juice is fine. The computer is very confident.
We made a shirt to commemorate the date that never was. It says "best by sep 31." Wear it on September 30, the last real day, and mark your calendar for the day after. You will be waiting a long time.
Get the Best By Sep 31 tee.
© 2026 Sort Of Ish™. All typos intentional.