Time of the Moon-th

I have 5 brothers and each think it is so funny to ask, when I get mad, if it is that time of the month for me. Well one day my oldest brother (22 at the time) wakes up pissed off for no reason and all day is being an ass. We are all in the living room and we were all sick of his attitude. Out of the blue my grandma walks to the bathroom and returns to toss a box of tampons and a bottle of Midol to him. Then told him to warn us when he be on his period next time.

THEY'RE NOT SUPPOSED TO KNOW

I feel like, as a guy, I should object to the image of a guy being consumed for asking that question, but actually it's both a fair and appropriate response. You just don't bring that $#!+ up with a girl.