Metro

Be-tray mine tonight

Valentine’s Day is prime time to two-time.

New Yorkers are most likely to seek an affair on the day after the holiday, according to a survey by a dating Web site that promotes infidelity.

Feb. 15 is the year’s biggest sign-up day at the extramarital sex site AshleyMadison.com. That’s because the holiday forces folks to evaluate their relationships, said the Web site’s CEO, Noel Biderman.

“It’s a self-reflective day. If Valentine’s Day felt hollow, you’re going to do something about it,” he said.

The number of new users who signed up on Feb. 15 last year was four times that of an average day, he said.

His “cyber-anthropology” study also found married women use the Web site most often on Mondays, while single gals seeking married men log in Thursdays.

The reason: Single ladies want to gear up for the weekend, while married ones need to get over it, Biderman said.

“Weekends are all about family — but if your needs aren’t being met, come Monday, you want to change that,” he said.

The study also determined that the average affair takes 36 hours — from first message sent until sex — and that most married men log in at 4:30 p.m. while women prefer 10 p.m.

Biderman noted married men also celebrate Valentine’s Day with mistresses on Feb.13, which he called “Mistress Day,” he said.