I understand 365 is not evenly divisible by 12. You get 30 with a remainder of 5.

Simple enough. Randomly pick 5 months and make them 31 days. You get a total of 365. Add 1 to a month for leap years.

But, that’s not what happened. They added 1 extra day to seven months. giving 367. So they had to steal 2 days from Feb. to get 365.

What was the reason for this unusual math?

Also, what was the logic for adding the extra day to Jan,March,May,July,Aug,Oct,Dec. Forcing everyone to memorize a poem to keep it straight?