Exactly how rare is Thanksgivukkah? Jonathan Mizrahi, who has a Ph.D. in physics from the University of Maryland and currently works for Sandia National Laboratories in Albuquerque, N.M., used the math software program Mathematica to chart the futures of the Jewish and Gregorian calendars. The output, he said, “produced no results other than this year.”
“I thought I made an error in the program, and I checked what I’d done, and everything seemed okay, and I pushed the year out further and further and further… and it still was telling me that it wasn’t ever going to happen,” Mizrahi said.
According to an analysis posted online by Mizrahi, the Jewish calendar “is very slowly getting out of sync with the solar calendar, at a rate of four days per 1,000 years.”
“This means that while presently Hanukkah can be as early as 11/28, over the years the calendar will drift forward, such that the earliest Hanukkah can be is 11/29,” Mizrahi wrote. “The last time Hanukkah falls on 11/28 is 2146 (which happens to be a Monday). Therefore, 2013 is the only time Hanukkah will ever overlap with Thanksgiving.”
“Of course, if the Jewish calendar is never modified in any way, then it will slowly move forward through the Gregorian calendar, until it loops all the way back to where it is now. So, Hanukkah will again fall on Thursday, 11/28… in the year 79811,” he added.
While American Jews prepare for Thanksgivukkah, whether or not 2013 is the first-ever occurrence of the “holiday” is up for debate. In 1863, President Abraham Lincoln enacted Thanksgiving to fall on the last Thursday in November. But Thanksgiving was changed to the fourth Thursday of November — not necessarily the last Thursday — in 1942 under President Franklin Delano Roosevelt, a move intended to extend the holiday shopping season. Using the former date of America’s Thanksgiving, the last Thursday of November, Thanksgivukkah would have occurred in 1888, according to Mizrahi.
Thanksgivukkah’s frequency can also depend on whether the first night or the first day of Hanukkah is used as an indicator. This year, the first candles of Hanukkah are lit the night of Nov. 27, while the first full day of the holiday is Nov. 28, corresponding with Thanksgiving. According to an analysis by Eli Lansey, who has a Ph.D. in Physics from the City University of New York and like Mizrahi used the Mathematica software program, the first night of Hanukkah will correspond with Thanksgiving in the years 2070 and 2165—much sooner than 79811, the next time after 2013 that Mizrahi said Thanksgiving would fall on the first day of Hanukkah.
No matter what metric one uses, Thanksgivukkah has garnered a significant following—Mizrahi’s mathematical analysis garnered about 100,000 page views online, to his “utter amazement.”
“When I first did this, I thought it was interesting, but I did not expect anywhere near the response I got,” Mizrahi said.