Nation What is Fastnacht Day or Fat Tuesday and why are people eating doughnuts? February 25, 2020 Brad Jennings, USA TODAY Comments Off on What is Fastnacht Day or Fat Tuesday and why are people eating doughnuts? Feb. 25 is Mardi Gras, National Pancake Day and in Pennsylvania, it's also Fastnacht Day or Fat Tuesday. Here's what to know about the tradition.