There are some cultures that do consider menstruation unclean (we can't really judge them on that) so there is an outside possibility this comes from one of the

There are some cultures that do consider menstruation unclean (we can't really judge them on that) so there is an outside possibility this comes from one of them... but somehow it doesn't strike me that way. I think it's just how this presented that makes it problematic. The crude terminology and focus on sex (and other areas of lacking sensitivity). Because on the one hand there is a solid/useful idea here. My girlfriends comment was "I'd maybe give it a shot if it was developed by a woman, or for a woman. This looks like something for a man, by a man" EDIT: I thought of a similar thing a friend of mine once had, he had a few girlfriends and recorded their periods on a calendar so he could check back and figure out who would be "free". This gives me the same impression :(