Oct. 15, 1978Sun1 (WS Game 5)1355 Oct. 14, 1973Sun1 (WS Game 2)1235 DATEDAYMLBNFLNBANHL Nov. 4, 2001Sun1 (WS Game 7)1374 Another sports equinox is in the booksDates on which all four major U.S. sports leagues (MLB, NBA, NFL and NHL) had at least one game Nov. 2, 2009Mon1 (WS Game 5)153 Oct. 12, 1980Sun1 (NLCS Game 5)1348 Oct. 17, 1971Sun1 (WS Game 7)1236 Oct. 21, 1973Sun1 (WS Game 7)1235 With nine NHL games, three NBA games, an NFL game and an MLB playoff game — made possible by the Chicago Cubs’ victory in Game 4 of the NLCS on Wednesday — Thursday is your (first) sports equinox of 2017.What’s a sports equinox? As my former colleague Reuben Fischer-Baum wrote on a couple of occasions, it’s when all four major U.S. sports leagues — the NFL, NBA, NHL and MLB — play at least one game on the same day. Historically speaking, it doesn’t happen often. There have only been 17 sports equinoxes in history, including Thursday: Oct. 15, 1972Sun1 (WS Game 2)1236 Oct. 27, 1985Sun1 (WS Game 7)1315 Oct. 22, 1972Sun1 (WS Game 7)1235 Oct. 14, 1979Sun1 (WS Game 5)1337 Nov. 1, 2010Mon1 (WS Game 5)133 NUMBER OF GAMES Nov. 1, 2009Sun1 (WS Game 4)1274 Oct. 19, 1980Sun1 (WS Game 5)1336 Nov. 1, 2015Sun1 (WS Game 5)1275 Oct. 30, 2016Sun1 (WS Game 5)1178 Oct. 19, 2017Thu1 (NLCS Game 5)139 Amazingly, there was a 15-year period without a single sports equinox, between 1985 and 2001. And after 2001, seven more years passed without it happening. But sports equinoxes have occurred much more frequently in recent years — six have happened in the nine years since 2008. They might become even more common in the future, thanks to Thursday-night NFL becoming a fixture, the World Series often running later than usual, and a new NBA scheduling policy this season that moved the season’s opening night up by a week and a half.If the Cubs can force Game 7 in the NLCS, Sunday will be another sports equinox. As will Oct. 29, if Game 5 of the World Series takes place. But even if those do happen, Thursday’s equinox will be the only one this season with the added bonus of college football — there are two FBS games tonight, including No. 25-ranked Memphis at Houston (A “Super Equinox”?). Good luck finding enough screens to watch it all!