As Thanksgiving and Chanukah merge into the excitement and frenzy of Thanksgivukah, American Jews are readying their pumpkin doughnuts and cranberry sauce-topped latkes.
And the hype is particularly heightened because Thanksgivukah, or so the hybrid holiday has been dubbed, is a once-in-a-lifetime occurrence.
Or is it? Depends who you ask.
One of the first to realize the overlap was Eli Lansey, a research scientist from New Jersey with a Ph.D. in physics, who posted on his blog in December 2010 about the calendar fluke happening this year, which has only happened before in 1888 and 1899 (before Thanksgiving switched from the last Thursday in November to the fourth Thursday).
“In 2013 Chanukah and Thanksgiving will fall out on the same day!” he wrote. “Ladies and gentlemen, when, in three years, lots of people start talking about this incredibly rare occurrence, remember: You saw it here first!”
Lansey wrote that, at least for the next 10,000 years, this would never happen again.
But the amazement really started to build when Jonathan Mizrahi, a quantum physicist from Maryland, wrote in a blog post in January of this year that the next time the holidays would converge was the year… 79,811.
But things get even more complicated than that. Since Jewish holidays begin in the evening, there are two more dates in the predictable future where Chanukah and Thanksgiving will overlap — for a few hours. In 2070 and 2165, Lansey noted, the first night of Chanukah will fall on Thanksgiving Day, so candles will be lit after everyone has had his fill turkey.
Speaking to The Jewish Week, Mizrahi said there is an “inherent ambiguity in saying that a day on the Hebrew calendar ‘coincides’ with a day on the Gregorian calendar… [since] every day in the Hebrew calendar touches two days of the Gregorian calendar. Normally when we match the two, we’re referring to the daytime part.”
But, he maintains, the next “true” overlap of Thanksgiving and Chanukah will not be for at least 70,000 years.
Rabbi Tzvi Freeman, a senior editor at Chabad.org, said this calculation is based on “a lack of understanding of the Hebrew calendar.”
“We’re dealing with three cycles here,” he told The Jewish Week. “There’s the tropical cycle, which is the actual cycle of the seasons as the earth tilts on its revolution around the sun. Then there’s the Gregorian calendar… and the Hebrew calendar.”
And despite the leap years that the Hebrew calendar has every two or three years to keep it in step, it still “gains one day on the Gregorian calendar every 233 years,” said Freeman. “If you would let that drift keep happening for a long, long time, eventually Chanukah would travel through all the seasons and catch up with the Gregorian calendar … in 79,811 years.”
According to Freeman, the current Hebrew calendar system is only set up to work about another 230 years before the holidays will no longer fall in the right season, but “Pesach must always fall in the spring.”
Originally, a central bet din, or religious court, in Jerusalem proclaimed the beginning of each month based on sightings of the moon. But after the diaspora, a computed calendar was set up to predetermine the dates of every holiday.
“At some point, we’re going to have to take additional measures” to correct the calendar, said Freeman. Before the calendar becomes obsolete, the Chabad rabbi said, “Moshiach is expected to arrive and gather the Jews from the diaspora. At that point we will return to establishing the calendar on a month-by-month basis.”
“But there certainly is no possibility that anyone will let Chanukah fall in July.”