Either A) New Years Day is a day of the week and your birthday changes every year (but in a vastly more predictable way; NYD will make next year’s dates one weekday ahead), or
B) New Years Day is a completely separate day and all years are identical, and you choose your birthday to be celebrated on the closest agreeable weekend if that matters to you
There is a pretty fucking solid one:
13 months exactly 4 weeks long. 364 days. Two unique days: New Years Day and Leap Day. Just put them together.
Now every month is the same length. Every numbered day is the same day of the week in every month for the whole year.
That’s the International Fixed Calendar?
People with their birthday on Monday are not going like that their birthday is always on Monday…
Either A) New Years Day is a day of the week and your birthday changes every year (but in a vastly more predictable way; NYD will make next year’s dates one weekday ahead), or B) New Years Day is a completely separate day and all years are identical, and you choose your birthday to be celebrated on the closest agreeable weekend if that matters to you