There's other mnemonics too, "I work 9-5 at the 7/11" and the observation that Jan 3 (normal) and Jan 4 (leap) can be remembered as, "3 times out of 4, it's January 3rd; the 4th, it's Jan 4th"

Silly mnemonics but it's something. The design about even number days all landing on March 0 / last day of Feb is a good and simple one. I don't know what Weekle is innovating -- instead of using an established system of mnemonics and calculations, he just presents his own table with no comments. Maybe his inspiration was to say, "hey guys, I made my own date calculation system" to impress people who don't know about Doomsday?