I’m not a talented enough developer to do this, but my idea for an app to fill this need I’m offering up for anyone to take and run with.
I’d call it “Haircuts”, and it can be used by anyone of any gender to track any regularly occurring event, such as getting a haircut, mowing the lawn, or menstruation.
The key would be for the functionality to exist for people who need it, but because more than just people who have uteruses could use it, the data doesn’t incriminate anyone.
My only requirements, if I were to be the one developing it, would be that the app would be free, open source, and all data is encrypted and remains on device only.