Use the 8 pieces to cover up everything except the current month and current day. For example, below is a solution for October 6:
Polypad Game Boards
Original Game Board
At this Polypad below, use the spinners to create a random day to use for the puzzle. Spin again if you land on an impossible date (May 37th for example).
Purchase a physical version of the puzzle from DragonFjord. Dragon Fjord Puzzles and Games holds an internationally design patent (EUIPO: 007690433; WIPO: DM/215118) for the Puzzle a Day. The Mathigon version is made with their permission.