Theirs is a permanent calendar, so dates will no longer “fall” on certain days of the week — they’ll be fixed in place. January 1 will always be on a Monday. Your birthday will fall on the same day of the week every year, forever, Hanke said.

The HHPC (its working title) is 364 days long, divided into four three-month quarters. Each month will begin and end on the same day every year. The first two months of each quarter are 30 days long. The third has 31 days.

In all, that’s 364 days distributed across 52 seven-day weeks, he said.

And to account for calendrical drift, when the length of the year doesn’t line up with the astronomical calendar (365.24 days, just about), its creators have added an extra week at the end of December every five or six years.