What is the phrase used by Tom and Donna on the day where they buy luxurious items for themselves?

One day each year, Tom and Donna take a day to "Treat Yo Self" and buy for themselves whatever makes them happy. Once, they invited Ben to join them, and it took him a while to get the true meaning of the day, but he eventually bought himself a full Batman costume.

Asked by Jason Forbes · Last updated 5 years ago · 8.6K views · SOURCE