Short: 13 Month Calendar
Don't you hate how difficult our calendar is to remember? 31 days in January, some weird number of days in February...and then if you try to track the cycles of the moon which is also tied to most women's periods, it gets complicated. What if, instead, we had 13 months of 28 days (totally 364 days) and then had one day (or two on leap years) that were holidays and not part of any month. What would you call this new month?