In classic Talmudic fashion, there are debates as to when Nittel Nacht actually begins. Chaim Saiman, a law professor at Villanova who specializes in Jewish legal theory, calls it the "Russian nesting doll" theory. Ask one question and several others pop out. You can't study Torah on Christmas Eve? Great … when does that start? Midday? Sunset? Nightfall? And since Orthodox Christians observe Christmas in January, there was actually a rabbinic debate about when to "celebrate" Nittel Nacht. Not surprisingly, extra-strict Jews decided to hedge their bets and observed Nittel Nacht on both nights.
So what would Jews do on Christmas Eve?
1) Tear toilet paper. I kid you not. Bear with me, as the reason is a bit convoluted: Observant Jews do not tear anything on the Sabbath as they consider it a form of "work." As such, they either don't use toilet paper on Saturdays (opting instead for pipe-clogging tissues) or pre-rip toilet paper before sundown on Friday. (I reluctantly confess, this is something I was exposed to while growing up the son of an Orthodox rabbi.) Since Jews were not allowed to study Torah on Christmas Eve, the rabbis still wanted the community to be doing something, um, productive. So they suggested people spend the time pre-ripping toilet paper for the entire year. I wish I was joking but, alas, I am not.
2) Play cards, play chess, spin a tiny top. Many synagogues held poker games on Christmas Eve; some say this is where the custom of spinning the dreidel on Hanukkah matured from, as a way for Jews to pass to the time.
3) Everything from managing finances to reading secular books to, get this, sewing. (That last one was actually a custom of the late Lubavitcher Rebbe, Rabbi Menachem Mendel Schneerson.)
It's obviously important to keep in mind that the often bizarre customs of Nittel Nacht were, as Rabbi Ari Enkin points out, "born out of political realities rather than theological ones. … Nittel Nacht comes to us from an era when relations between Jews and Christians, the Church and Judaism, could be described as 'tense' at best. We are fortunate to be living in a day and age where relations between these two groups have flourished immensely."
I couldn't have said it better. This is an era of remarkable religious tolerance. Hanukkah menorahs get erected next to Christmas trees at the mall. Kwanzaa gets its own postage stamp. The Gap's holiday commercials name-check winter solstice. Which is why most Jews no longer celebrate (or even know about) Nittel Nacht. It is, on many levels, a holiday far past its expiration date.
Regardless, because it's the nature of the beast, there will be Jews gone rogue: holding poker tournaments and furiously ripping toilet paper this Christmas Eve. And to them I simply say, "Merry Nittel Nacht, and to all a good night."