... you'd know that a woman does not forget when she has her period. At least I don't know a single woman who does not know about this.
@Alyra : I will not bet on this ^^ She knows when she had it yes, but about 3 weeks later, that's not always the case, from a few days to one week, she doesnt know exactly. At least, I know one woman who doesnt know exactly
But is that a subject you talk a lot with girls ? ^^
Imagine : "Hi, how are you ? By the way, when was your last period ? (don't worry it's only for personnal stats)" oO