Time difference

A simple question sent me down a rabbit hole this morning: what is the time difference between Houston and London?

At the moment the difference is six hours. But how will that change when Daylight Saving Time ends this year. Wait a minute, will Daylight Saving Time end this year?

I wasn’t even sure whether we were on DST until I asked my wife a few days ago. “Spring forward, Fall back. It’s been Fall for a month now. Did we fall back?”

The US Senate passed the “Sunshine Protection Act” last year that would have eliminated changing times (Yay!) by permanently staying on DST (Boo!). Whatever happened to that? Are we about to fall back or not?

Turns out the House of Representatives never passed the bill, so  things will stay as they have been. Apparently the Senate didn’t seriously consider the Sunshine Protection Act. According to Wikipedia,

In 2022, the Senate passed the bill by unanimous consent, although several senators stated later that they would have objected if they had known that the bill could pass.

OK, so when does the time change in the US? It’s always a Sunday, but which one? Again according to Wikipedia,

Since 2007, in areas of Canada and the United States in which it is used, daylight saving time begins on the second Sunday of March and ends on the first Sunday of November.

Alright, now what about London? Europe has “Summer Time,” which is the same idea as Daylight Saving Time. Summer Time ends on the last Sunday in October.

At the moment, London is 6 hours ahead of Houston. This Sunday, October 29, London falls back an hour and the difference with Houston will be 5 hours. Then the following week it goes back to 6 hours.

In the process of looking into this, I found out that between 1941 and 1945, and again 1947, there was something call British Double Summer Time in which clocks sprung ahead two hours.

Time zones are surprisingly complicated, though mostly for good reasons. I would not recommend abolishing time zones (except for anything done on a computer, in which using UTC internally is the only way to go). But Daylight Saving Time / Summer Time is ridiculous. It made more sense years ago than it does now. Now there is more variety in individual work schedules, and there is more need to coordinate with people outside your time zone.

7 thoughts on “Time difference

  1. Until 2007 the fall change in the US was on the last Sunday of October. My understanding is that the candy lobby pushed for moving it back a week so that Halloween would be in the daylight savings time period, which they thought would increase candy sales for trick-or-treating. But it seems to me that people don’t start trick-or-treating until it at least starts getting dark, so they got it wrong!

  2. There was also an argument that changing the date would save energy, though it had the opposite effect.

    Maybe saving energy was a politically acceptable cover for satisfying candy manufacturers.

  3. And then there is nasty moment when one realizes that when the clock in the Northern Hemisphere spring forward, the ones in the Southern Hemisphere fall back. And it all depends on the politicians in power. It’s a right mess!

  4. Good summary and still incomplete. There is no synchronized DST in the United States, Arizona and Hawaii don’t do it.
    In Europe, Switzerland did not join at first only to find that life gets much more complicated if everyone around you does it.
    As you correctly point out, the period ends on different weekends in the US and the EU. See “globalization”.
    When it come to time zones, my “favorite” one is the time difference between Adelaide and Melbourne, half an hour!
    Conclusion: sigh.

  5. In the United Kingdom, and not knowing that the time change occurred… took train to London to take flight home and discovered en route that we were going to be at *high* risk to miss the international flight.


  6. Between somewhere in the US (possibly excepting Arizona, haven’t done the math) and New Zealand there are three possibilities. Both countries observe a form of daylight savings time, but it goes the other direction in the Southern Hemisphere.

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