Tuesday, February 05, 2013

Turkey and Latkes

Got the following from a friend.  Any Jewish calendar aficionados out there able to corroborate this?

The first day of Chanukah coincides with Thanksgiving, on 11/28/2013.

It turns out that it has never happened before...and it will never happen again.
Thanksgiving is set as the fourth Thursday in November, meaning the latest it can be is 11/28.

11/28 is also the earliest Chanukah can be.
The Jewish calendar repeats on a 19 year cycle, and Thanksgiving repeats on a 7 year cycle.

You would therefore expect them to coincide roughly every 19x7 = 133 years.
Looking back, this is approximately correct – the last time it would have happened is 1861.
However, Thanksgiving was only formally established by President Lincoln in 1863.
So, it has never happened before.

Why won't it ever happen again?
The reason is because the Jewish calendar is very slowly getting out of sync with the solar calendar, at a rate of 4 days per 1000 years (not bad for a many centuries old calendar!)
This means that while presently Chanukah can be as early as 11/28, over the years the calendar will drift forward, such that the earliest Hanukkah can be is11/29.

The last time Hanukkah falls on 11/28 is 2146 (which happens to be a Monday).
Therefore, 2013 is the only time Chanukah 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, Chanukah will again fall on  Thursday, 11/28 ....
...in the year 79,811.                                          
Just found a link with graphical info showing Hanuaka and Thanksgiving overlaps....(and perhaps the initial article above)


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2 comments:

Anonymous said...

What you have there is the work of a serious calendar geek. If I did not recognize this as BZ's work, I would have referred you to hi.

D.C. said...

It's correct. I wrote a quick program to check it after I got this as an e-mail last week. The initial e-mail that I received had said that the *only* time after 2013 that we would have a November 28 Chanukah would be in 2146, which is incorrect. That is the *last* time it will happen, though, and none of the times before that are on Thursdays either.

While we're on the topic, I will offer 20 points (redeemable for bragging rights) to whoever can correctly answer the following question (which is geared to the Israeli readers).

Another anomaly of this "very early" Jewish year is that we will have the seder in sha'on choref (Standard Time). Assuming the current rules (passed into law a few months ago) remain in effect, when is the next time this will happen?

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