How does this happen?

Cleaning out the fridge and at the back is an unopened jug of buttermilk I bought the other week to make some bran muffins.  Haven't got around to making them yet so I thought I'd better move it to the front as a reminder.  Haven't had bran muffins in a few months and have a bit of a hankering for them.

It is November.  Apparently I haven't had bran muffins in longer than I thought.

Well, off to the store to buy a new jug.  Oh, and here's my recipe.