OKCupid might send out email blasts telling you to log in during a rainstorm because that's when the site's apparently busiest in any given location, but Nielsen wants you to know when the best time is to log in, period. For the dating website, the uptick starts at 6 PM, peaks at 9 PM and falls off sharply starting at 10 PM according to The Huffington Post. Those rainy-night emails? In my case, they arrive just after 7 PM. Surprisingly, the more fling-favorable Tinder is busiest at the same times as OKCupid in terms of unique audience, with over 50 percent of users beginning their swipe-fests during primetime.