Sunday, September 16, 2007

Fall back

Last night, Israel switched off of Summer Clock (aka Daylight Saving Time) onto Winter Clock. This means that until the US switches (which is now in November, because Congress decided that it was a good idea to have an extra week of waking up in the dark), the time difference between the US and Israel will be one hour less. I.e., we'll now be 6 hours ahead of EDT and 7 hours ahead of CDT.

Until the passage of the Israeli Daylight Saving Law in 2005, there was no fixed algorithm for the beginning and end of DST, and so the Knesset would fight over it every year as if summer had never happened before and would never happen again. Now, it is guaranteed that Winter Clock will begin before Yom Kippur, so that the fast is shorter.

Um, right.

SHF and I used to debate this endlessly. I would argue that the fast is 25 hours no matter what, so if the fast ends an hour earlier, then it also starts an hour earlier, so you don't gain anything. SHF would say that it still makes a difference, because how hungry you feel depends on how much time has elapsed since you woke up. I would respond that the time from when you wake up until the end of the fast isn't going to change, if you're now waking up an hour earlier because services are starting earlier due to the clock change. This assumes that you care about getting there on time. If you don't, then sleep as late as you want, and the clock change doesn't matter. One might respond that the time you'll naturally get up (assuming you're not getting up earlier due to earlier service times) is the time that you're used to getting up, and so the time from when you get up until the end of the fast will indeed be shorter. I would respond that if you just switched off Summer Clock a few days ago, then your biological clock hasn't adjusted yet, so you're not going to instantly start waking up at a different time (unless you want to, which again is a choice you can make without changing your clock). In the end, perhaps the only convincing argument for how the clock change makes the fast easier is psychological sleight of hand: you think it's only 6:00 instead of 7:00.

The one thing that this clock change does accomplish is make Tzom Gedaliah effectively shorter. Yes, the time from sunrise to sunset is unchanged, but if you're not getting up before sunrise to eat, then the time from when you last ate (before going to bed) until the end of the fast is going to be shorter.


  1. Except that the clock change happens on motzei shabbat shuvah, which usually doesn't fall before tzom gedaliah. You just got lucky this year.

  2. Except most shuls don't change their start time because of the DST shift. If the shul generally has a break between musaph and mincha then the mincha start time is shifted and the length of the break changes. If the shul doesn't have a break then the Rabbi and Cantor just adjust the service so that you go straight through either way. So changing what time sunset is does affect the total time between the beginning of shacharit and the end of the fast.

  3. At the other end of the year, the religious wanted Summer Time to begin after the Pesach nite seder so that it starts earlier and the kids don't fall asleep too soon. Every year their was a lot of demogaguery on the issue and numbers were thrown around claiming "millions of shekels" are supposedly saved for each extra day of summer time that is in force. An electric company official admitted in a radio interview that the numbers were all made up.
    Ultimately, a compromise was reached and the religious gave up Pesach to get the earlier ending to Yom Kippur and I think that was the correct decision (it also gives everyone extra time to prepare the Pesach seder). I do believe that having it end earlier helps psychologically, if not physiologically.

    G'mar hatima tova.

  4. I suspect the difference is all in my head; that said, it really does feel easier when the fast end-time is an earlier number.

    I'd quote Dumbledore here, except my little sister took all the HP books to college.