When you're a girl and you are in a situation when you'll have to go swimming several times, such as at a summer camp, and you don't want to. You tell them you're on your period for an undefinable amount of time (such as however long this situation lasts). Call it cronohemotosis.
Osis-- abnormal/increased when blood is involved
Girl: "I'm not even planning on going swimming this year, and there's no way in hell I'm putting on a swimsuit. No way. I'll say I have my period and that it lasts for two months. Yup. It's called cronohemotosis. Totally."