For those who live where the Polish heritage is strong or dominant, such as Detroit or Chicago, today is Pączki Day (pronounded "punch-key"). Simply put, a pączki is very much like a high cholesterol, high calorie (and therefore, much tastier) filled doughnut. It's traditionally served on "Fat Tuesday"--the day before Ash Wednesday--as a way of both cleanining out the cupboard of foods forbidden during Lent (according to the older Catholic rules), and gorging oneself one last time before Lent.
So you shouldn't save the leftovers for another day. If you don't eat them today, you should throw them out.
However, I have a better solution. Take your leftover pączki to your local Orthodox church, or give them to your Orthodox neighbor. Why? Because our Lent doesn't begin until next week.