If a year had 13 months

That’s the basis of the International Fixed Calendar.

• Every year has 13 months and every month has exactly 28 days
• The extra month is called “Sol” and it comes between June and July
• Every month begins on a Sunday and ends on a Saturday
• That means that “the 17th” for example is always a Tuesday, regardless of month or year.

Of course, 13×28=364 which leaves one missing day. So to fix that, there’s a freebie holiday at the beginning of the year called Year Day. Year Day (like Leap Day) doesn’t belong to a week. It comes between Saturday and Sunday.

The main downside (besides the obvious fact that switching to it as a society would cost a ridiculous amount of time and money) is that 13 is a prime number, so things that happen quarterly or twice a year don’t divide cleanly.

Just thought it was interesting!