Tuesday, 27 October 2015

Daylight Saving Time

I really don't know why we have Daylight Saving Time - it just causes hassle, and does not do anything useful - we have plenty of daylight in the summer, and we move that daylight around (relative to when we work) by an hour. Makes no sense at all.

But we did have slight fun yesterday flying from Texas to New York. The problem being that we were not sure if they were different time zones or not. Yes, googling would have worked.

Of course, all of the iPhones and Apple watches switched and advanced an hour. But my Casio watch insisted it we the same time. This would have been fine if not for a clock on the wall at the hotel telling time in New York, Paris, Tokyo, etc, which agreed with my watch! It was the only clock we could see in the hotel. We ended up having to ask someone the time to be sure.

The problem - bloody daylight savings time. On my watch I adjusted the world time until it matched where we were in Texas, and it said "NYC", so I assumed time zones must be the same. What I failed to spot is that the "DST" setting needs to be adjusted manually as well (per time zone). Had I done that I would have realised I needed to set to some other time zone "CHI"? So when we got to NYC it was saying the wrong time but claiming to be "New York City" time. Of course, the "DST" indicator is not obvious when "un lit" so the mistake is not obvious.

What is worse is that it has the UK time wrong as well. It had DST set to AUTO, which works perfectly when in the UK, but does not switch DST based on the "rules", but on the radio signal (which it cannot get whilst here in US). So I had the local time set a hour back and the UK time an hour forward on a watch that normally "just works".

To add to the fun, in New York, it is still DST until this Sunday, but not DST in the EU. Anyway, at least we are only 4 hours adrift from UK, not the 6 of when we landed.

I have finally managed to get my watch set right! Time for some breakfast.

15 comments:

  1. Daylight savings time does have one useful side effect. Forcing everyone to change their clocks twice a year means the clocks are reasonably correct. My mains timeswitches drift by about 5 minutes between each DST change, so if it wasn't for DST I'd have to set another date to fix clocks eg. Easter.

    I try to buy stuff that either receives the UK atomic clock by radio or uses internet time via NTP. But I've yet to find a mains timeswitch that does either.

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    1. Mains is usually OK as they adjust cycles to ensure they average correctly, so any device using mains 50Hz to control its time should "just work". Would be fun if they tried to adjust mains cycles for BST though :-)

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    2. These are digital mains timeswitches. They have battery backup so don't lose time while the mains is off, but the downside is this means they're crappy cystal based time source so not remotely accurate.

      I found the mechanical mains ones switched on or off very slowly and generated a lot of mains arcing, which interfered with Freeview and FM reception. So I replaced them with digital mains timeswitches.

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    3. It is a shame they do not pull a signal from the 50Hz as a reference though. That is how I would have designed it :-)

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    4. Indeed, the long term average of 50Hz mains in the UK is extremely accurate.

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  2. I never rely on a timekeeping device that doesn't implement the Olson database. I usually have at least two with me.

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  3. What, never? Your central heating system and wall clocks and phone clocks use the Olson db? (... actually, given *your* house, quite possibly they do. But mine don't, and I have no idea how to get them to do so. And as for the mechanical clock I learned to tell the time from, which predates the Olson db by about two hundred years...)

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  4. The key word is "rely". Sadly, my wall clocks are not driven off NTP (I think I will have to build one myself in order to make this happen at a sensible price), but I don't trust them as sources of time either. If I'm in any doubt at all, I look at my Kobo, laptop, or one of the IP-phones.

    (All right, for "implements the Olson db" read "implements or is driven directly by something that implements".)

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    1. Oh, agreed. I rely on my watch or my NTP-running computers first and foremost -- and my watch is synched to the radio signal (the one which used to be the Rugby signal before it moved, uh, somewhere else). Of course my watch reliably fails to get a signal on days when the clocks change, leading to me noticing hours too late :/

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    2. I'm happy enough with a device that I know definitely does not, or a device I know definitely does. What catches me out is things like dumbphones and Windows that might or might not get it right...

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  5. I think my comment just vanished. Apologies if this shows up twice.

    My wallclocks and such are not NTP-linked (to do this at a sane price I'll probably have to build my own), but I don't rely on them - if I'm in any doubt I look at my Kobo, or a laptop, or one of the IP-phones.

    All right, for "implements the Olson db" read "or is driven automatically by a machine that implements".

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  6. In some ways I would prefer GMT+1 all year round as it would avoid having to cycle home in the dark - hate the sudden change. If everyone worked 8 to 4 instead then GMT would make more sense but they dont

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  7. RevK: George Bush Jr. changed the dates the US alter their clocks, so in the Autumn they change a week after us, in the Spring it's something like 3 weeks before us, and during those overlaps NY is 4hrs behind us instead of the usual 5.
    I'd be happy if we stuck to GMT throughout the year - at least you know when the Sun is overhead! If people want more daylight at one or other end of the day, they'll have to adjust their timings. The original idea of having more time for farmers is bogus - farmers work according to the daylight, or ignore it and have floodlights on their tractors!

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    1. Even before 'W' interfered, US dates for DST were not the same as the EU. They used to be first Sunday in April for going forwards whereas we are last Sunday in March. We used to agree going forwards.

      'W' changed the dates claiming it would save energy by using more daylight. Moron.

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  8. "'W' changed the dates claiming it would save energy by using more daylight. Moron."

    To be fair, it wasn't *his* stupidity there, and the official figures afterwards did claim the changed dates did indeed reduce electricity consumption very slightly.

    I was happy to find that several places in the US have taken initial steps towards opting out of DST, as Arizona, Hawaii and the various territories (Puerto Rico etc) already do. Let's hope that catches on.

    This page is the second place this month I've seen someone repeating the erroneous claim that it's GWB's fault that the US changes on a different date to the EU. Nice to see it getting rebutted promptly, of course.

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