Period tracking methods?

Sophia
I was wondering if anyone else uses monthly bills or stuff like that to track their period ๐Ÿ˜‚๐Ÿ˜‚๐Ÿ˜‚ I always know that when my phone data resets every month, it's time to keep my cup handy!!! (This app helps too, of course ๐Ÿ˜) What do you guys use as a reference point?