I’m amused by all the attention lavished on PMSbuddy, a free online service for men to keep track of their [wife’s, girlfriend’s, mother’s, sister’s, daughter’s] menstrual cycles. Advertised as a way of giving guys a “heads-up” at “that time of month,” the site tracks a woman’s cycle and predicts when she might be her “most irritable…when things can get intense for what may seem to be no reason at all.”

A few reactions:

1. From a reproductive standpoint, it’s actually in a gal’s best interest to keep her partner in the dark about her fertility cycles. As described in BLONDES, there are reasons why women evolved to have concealed ovulation. If your partner knows when you’re fertile, he knows when to guard you. (Of course, we inadvertently advertise our fertility anyway, albeit subtly.) And if he knows when you’re not fertile, he might go out and sleep with someone who is. Evolutionarily speaking, of course.

2. Women’s tolerance for the PMSbuddy proves that we live in a post-feminist era. Many women are genuinely OK with the concept. Yes, our moods fluctuate with our hormones — so what? However, judging from reactions online, some women are shouting sexism — and I wonder if there is a generational difference. These women are offended by the idea that their moods are predicted by hormones, at least to the degree that anyone else would notice. It suggests we have less control over our bodies and behavior than we’d like. Worse, some think PMSbuddy’s premise is that women are unstable and irrational in ways that men are not.

3. But the latter just isn’t true — that is, men are also hormonally volatile — and acknowledging this makes all the difference. As I discuss in the book, men’s testosterone levels rise and fall dramatically depending on their situation or context. Sometimes men have their own predictable cycles. Want proof? Take SuperBowl Sunday. Is your man a Steelers or Cardinals fan? How his team fares may predict whether his testosterone rises or plummets, which in turn could affect his mood for the next day or two.

Perhaps it’s time for TBuddy: a service to predict your man’s testosterone-based mood swings at “that time of season,” based on the game schedule and sports forecasting services. (A daily TBuddy may predict mood by taking into account the Dow and NASDAQ market predictions.)