1/n #Hanukkah comes super early this year – it starts tonight! – and in fact, this is the earliest that it *can* occur. Let’s talk about why that’s so! (thread 🧵 ) #Hanukkah2021
2/ The date of #Hanukkah is determined (no surprise) by the Hebrew calendar, not by the Gregorian calendar. More specifically, Hanukkah begins on the 25th day of the Hebrew month of Kislev...
3/ The Hebrew calendar is “lunar-solar,” which means it uses months based on the cycle of the moon’s phases, but also attempts to synch up with the annual cycle of the seasons…
4/ It does this by using months of slightly different lengths (they can run 29 or 30 days); and also by varying the number of months in a year (the year can contain either 12 or 13 months, with the extra month being inserted in 7 out of every 19 years)...
5/ Because of this variability, Kislev can start as early as November 3 or as late as December 2, and so the first day of Hanukkah can come as early as November 28 or as late as December 27...
6/ It should be noted that the Hebrew calendar is slightly out of synch with the Gregorian calendar: The Gregorian calendar is based on an average year of 365.2425 days, while the Hebrew calendar uses the slightly less accurate approximation of 365.25 days...
7/ Ever since the Gregorian reform was introduced, more than 400 years ago, the two calendars have been drifting apart by about 11 minutes per year. (This is also true of the Julian calendar.)
8/ Because of this, although #Hanukkah has occasionally overlapped with American #Thanksgiving – the last time this happened was 2013 – it will in fact never happen again! (Barring a reform of the Hebrew calendar, which could happen one day.)
9/ For more detail, see @JoelMHoffman's interesting article from 2013: huffpost.com/entry/hanukkah… And for more on the physics and philosophy of time, see my 2008 book, "In Search of Time." :) danfalk.ca/in-search-of-t… And #HappyHanukkah!!
• • •
Missing some Tweet in this thread? You can try to
force a refresh
