Film-Tech Forum ARCHIVE: Daylight saving time.

This is topic Daylight saving time. in forum Film-Yak at Film-Tech Forum ARCHIVE.

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Posted by Stephen Furley (Member # 1277) on 09-09-2016, 07:59 AM:

On what date do the clocks go back in the USA this year? Is it the same in all states? I know that it's usually not the same as here in the UK. We're setting up a live Skype video interview with a director, and so may need to take this into account.

Posted by Martin McCaffery (Member # 37) on 09-09-2016, 08:08 AM:

According to my calendar: Sunday, November 6 is the last day of DST.

I think all states go back a the same time, but not all states go on to start with.

Posted by Mike Blakesley (Member # 26) on 09-09-2016, 09:44 AM:

It does end on the 6th, but at 2:00 AM that day.... So, set your clock back when you go to bed on the 5th.

Posted by Randy Stankey (Member # 64) on 09-09-2016, 05:55 PM:

The end of Daylight Saving Time used to be an event, back when I was a kid.

My parents used to own a bar, back then. According to Pennsylvania law, bars must close at 2:00 a.m. Since 2:00 became 1:00 when DST ended, people had an extra hour to drink.

My father would stand by the clock and everybody would count down the seconds like it was a miniature New Year's Eve celebration.

We usually made a fair chunk of extra change in that extra hour. [Big Grin]

Posted by Stephen Furley (Member # 1277) on 09-10-2016, 03:24 AM:

Thank you. Both countries will still be on Summer time, so we won't fall into that week when one has gone back but the other has not. Eastern will be the usual five hours behind us, and pacific eight hours. All I need to do now is find out where the director will be at the time.

We did our first one of these last year, it generally worked very well, and the picture looked better than I was expecting. At the time we had no network in the auditorium, so had to take the glass out of one of the ports and drop a long cable through it, but we now have fibre to behind the screen, and copper from there to the auditorium trough. Used fibre because it has to run past some electrically very noisy equipment, lighting ballasts, on the way.

Did the last one in a hurry, and have learned a few lessons, one of them being to put a plain background behind our interviewer; there are some free-standing display screen things just up the corridor, I'll grab one of those.

Posted by Leo Enticknap (Member # 534) on 09-10-2016, 11:31 AM:

quote: Stephen Furley
Thank you. Both countries will still be on Summer time, so we won't fall into that week when one has gone back but the other has not.

It can be between one and three weeks, depending on the year. This used to cause no end of confusion timing phone calls with relatives in the UK, until I found a widget for my phone that displayed the current Pacific Time and UK Time next to each other, which automatically adjusts accordingly during those two periods in the year when the gap is not eight hours.

BTW, there is a move in California to abolish DST, though the consensus of opinion seems to be that it's unlikely to succeed. The length of the days here are so much more even than they are in northern Europe that, IMHO, it really doesn't make any difference; but maybe that's not so much the case in the north of the state. San Diego and the Oregon border are something like 700 miles apart, after all.

Slightly OT, but this book is a fascinating account of the subject, which, before reading it, I had no idea was so politically controversial.

Posted by Stephan Shelley (Member # 8587) on 09-10-2016, 11:39 AM:

In the USA it is now 2am the first Sunday in November. Not all states or even locals go to Daylight Savings in the first place. Arizona and Hawaii are two states that do not.

In California the bars are not allowed to stay open an extra hour on the morning it changes as it is 2am when it happens the bars have to be closed by 2am. ABC's thinking is it reached 2am before resetting to 1 am so you need to be closed.

Posted by Leo Enticknap (Member # 534) on 09-12-2016, 11:40 PM:

quote: Stephan Shelley
Not all states or even locals go to Daylight Savings in the first place.

The Uniform Time Act of 1966 removed the ability for cities and counties to set their own time zones and/or individual DST policies: only states can decide whether to use DST or not (according to Wikipedia, only Arizona, Hawaii and some US overseas territories opt not to). Time zone boundaries and the start and end dates for DST can only be set by the federal government.

Before that chaos ruled, with entities as small as a small city being able to decide what time zone they wanted to be in, whether or not to use DST and if they did, when it started and ended!

quote: Wikipedia
From 1945 to 1966 U.S. federal law did not address DST. States and cities were free to observe DST or not, and most places that did observe DST did so from the last Sunday in April to the last Sunday in September. In the mid-1950s many areas in the northeastern United States began extending DST to the last Sunday in October. The lack of standardization led to a patchwork where some areas observed DST while adjacent areas did not, and it was not unheard of to have to reset a clock several times during a short trip (e.g., bus drivers operating on West Virginia Route 2 between Moundsville, West Virginia, and Steubenville, Ohio had to reset their watches seven times over 35 miles).

In summer 1960 April–October Daylight Time was nearly universal in Pennsylvania, Maryland, Delaware and states east and north of there. In Minnesota, Iowa, Missouri, Kentucky and Virginia and states north and east of there, some areas had it and some did not. Except for California and Nevada, which had April-Sept Daylight Time, 99% of the rest of the country used Standard Time year-round. (The Official Guide says "State law prohibits the observance of "Daylight Saving" time in Kentucky but Anchorage, Louisville and Shelbyville will advance their clocks one hour from Central Standard time for the period April 24 to October 29, inclusive.")

In the middle 1960s the airline and other transportation industries lobbied for uniformity of Daylight dates in the United States.

One local example to here was Palm Springs, which had its own time zone, 30 minutes behind the rest of California within the city limits, because the large mountain to the south-west meant that it starts to get dark earlier. From the way the book I linked above describes it, before 1966, if you strayed much beyond the big metros and heavily populated areas, you could never be totally sure what the time was. Given that there were no smartphones or other ways of finding out definitively and accurately what the time was in your current location (other than calling the speaking clock from a landline), that must have been very confusing for everyone.

Posted by Dustin Mitchell (Member # 372) on 09-13-2016, 09:20 AM:

I find it interesting that the airlines had to lobby congress to standardize time. This isn't a comment about the role of government, simply a musing that time zones and standardized time in the US were originally set up by and for the railroads. It didn't matter what the 'local' time was, the train would arrive (or was supposed to, at least) at the time set by the railroad. I guess the airlines of the 1960's probably didn't have nearly as much power and influence as the railroads of the late 1800's, so such a unilateral move wasn't practical.

Posted by Marcel Birgelen (Member # 6801) on 09-13-2016, 05:05 PM:

Years back someone asked me to write a piece of software for an embedded system that should be able to account for all the possible implementations of "Daylight Saving Time" around the globe and that thing drove me nuts. Those people in charge can't just settle on an easy to pinpoint date, but it often ends up like the first Saturday or the last Sunday of a particular month. Which might be doable in a high level language, but isn't all that practical in some basic assembly language and memory constrains still calculated in kilobytes.

Luckily, most operating systems nowadays do have built-in functions and they regularly update their database, because governments around the world keep changing this stuff around all the time.

For an actual overview of DST dates around the globe, check out this page.

Posted by Randy Stankey (Member # 64) on 09-14-2016, 08:18 AM:

quote: Stephan Shelley
In California the bars are not allowed to stay open an extra hour on the morning it changes as it is 2am when it happens the bars have to be closed by 2am. ABC's thinking is it reached 2am before resetting to 1 am so you need to be closed.

The time goes from 01:59:59 then back to 1:00:00.
It never reaches 2:00:00 until an hour later.
It would have been 2:00 but for the time change.

There was much debate on the subject, in the bar, those days. [Wink]

Posted by Dustin Mitchell (Member # 372) on 09-14-2016, 01:43 PM:

A nifty argument, Randy, but one I don't think you'd actually win.

Federal Statute:
https://www.law.cornell.edu/uscode/text/15/260a
Note that DST ends AT 2 a.m. The logic that DST ends on 1:59:59 a.m. and that 2:00:00 a.m. does not happen (at least until another hour has passed) seems misguided to me. The way I read it, the clock strikes 2:00:00, but before striking 2:00:01 it turns back to 1:00:00. If the clock gets turned back at 1:59:59 to 1:00:00 we lose a second.

But, to be fair, you're not the only one that thinks the California law is confusing:
http://www.southerncaliforniadefenseblog.com/2008/04/ca_legislature_time_change_has.html

Posted by Randy Stankey (Member # 64) on 09-14-2016, 02:07 PM:

If DST ends at 02:00:01 then there must also be a leap second to replace the second lost at the time change.

The only way to preserve the continuity of time without a leap second would be for the time to go from 01:59:59 to 01:00:00 without ever reaching 02:00:00.

Posted by Dustin Mitchell (Member # 372) on 09-14-2016, 02:32 PM:

I suppose it depends on how many thousands/millionths of a second you want to get down to. The way I read it, the change happens at 2 a.m. If you say the clock never reaches 2 a.m., how can the change happen? I say it rolls over from 1:59:59 to 2:00:00 and instantaneously reverts to 1:00:00; it's technically 2:00:00 for a nanosecond (never reaching 2:00:01 and causing a second to be lost).

But hey, I'm originally from Wisconsin, where it was definitely interpreted to be an extra hour of bar time. The last Saturday in October was usually when 'bar' Halloween was, so in my early/mid 20's when DST ended on the last Sunday in October, I definitely took advantage of that extra drinking time [Smile]

.

Maybe we can bring theoretical physics and the theory of relativity into the mix? [Wink]

Posted by Randy Stankey (Member # 64) on 09-14-2016, 03:02 PM:

The clock progresses as follows:

...01:59:58...
...01:59:59...
...01:00:00...
...01:00:01...

It never gets to 02:00:00. Not even for a millisecond. If it did 02:00:00 would be duplicated. Then you would have to add an extra second to the day. States do not declare leap seconds. Only the Naval Observatory can declare a leap second.

Posted by Dustin Mitchell (Member # 372) on 09-14-2016, 03:35 PM:

Time and Date seems to follow your incorrect logic, I'll have to write them to correct their flawed reasoning when I have time:
https://www.timeanddate.com/time/dst/transition.html

[Big Grin]