While talking with my friend Cody about the possibility of reusing calendars every few years due to them repeating, we wondered if every possible calendar could occur, and how many years one would have to wait to have all the possible calendars. When I got home, I made a spreadsheet that identified the pattern.

This pattern would continue until 2099. The rules for leap years would make 2100

**NOT**a leap year and the pattern would start over again in 2101. The rule for leap years is that every year that is divisible by four, except for multiples of 100 that are not divisible by 400**ARE**leap years.