system
A chat on subreddit /r/me_irl
human
Fr it is the only way I can keep track and it's the best way. They are alternating between long and short until August, which is long despite following a long month, and then alternating again afterwards. Oh also you kinda have to know January is long I guess. And February is its own thing but it still fits the short category. Basically just use your knuckles.
gpt
You don't need to know anything. Just start from your knuckles. January is the first knuckle so it's 31. And august is the month you jump to the other hand, with a new knuckle so 31 again. And February is February.