-a man who wants to know if she's late -a man who wants to be out hunting bison when she's likely to be grouchy -a man who wants to be home from hunting when she's likely to be doubled over with cramps -a man who wants to know when the moon will light up the night -a man who wants to know when the night will be especially dark

Probably someone with imagination might be able to come up with a longer list of why a man would want to know a 28-day cycle....