There's always some confusion when this comes up, so I thought I'd make one place to rant about it...
This is more for the benefit of people living outside of North America (specifically the US and Canada) and needing to know just how Daylight Saving Time occurs here, since most deck releases, Kickstarter projects, eBay auctions, etc. occur here and use our time conventions.
Almost everyone in the world is familiar with "Summer Time" or "Daylight Saving Time" (yes, it's "Saving", not "Savings" - it's not a bank account!). Clocks go ahead in the spring by an hour, fall back in the fall by an hour.
In the US and Canada, most of those two countries observe Daylight Saving Time (DST), with the major exceptions being many Native American territories and the state of Arizona, which remain on Standard Time all year long. Unlike the rest of the DST-observing world, however, our governments have seen fit to extend the duration of DST to the point where we're on Daylight Time more than we are on Standard Time, making it the de facto standard! For most of the world that changes their clocks, they "spring ahead" in late March or early April and "fall back" some time in October - but seeing how special we are in North America, we start DST on the second Sunday in March and don't end it until the first Sunday in November. Also, unlike in the European Union, we change time at 02:00 AM local time, with the change rolling from time zone to time zone - the EU mostly uses 01:00 UTC as the time to change across all EU time zones. (At least that's what Wikipedia says, and I'm sticking to it!)
And this doesn't even begin to touch the changes that occur on the southern half of the world! But for the rest of the world, it's not much of an issue - in fact, the majority of the world DOESN'T observe DST or Summer Time. Much of Asia doesn't use it, and most nations near the equator don't because they remain relatively unaffected by seasonal changes in relation to the duration of daylight per day.
But back to my point... Here's how DST affects time in the most populous time zones in North America - Pacific (California, western British Columbia), Mountain (Colorado, Alberta), Central (eastern Texas, western Ontario) and Eastern (eastern Ontario, New York). The UTC listing in the right column is the standard and is unaffected by Daylight Saving Time.
This year, the second Sunday of March is 10 March 2013 (a.k.a. tomorrow!). All times shown in
red are in Daylight Saving Time.
Pacific Time | Mountain Time | Central Time | Eastern Time | UTC |
10:59:59 PM (Sat.) | 11:59:59 PM (Sat.) | 12:59:59 AM | 01:59:59 AM | 06:59:59 |
11:00:00 PM (Sat.) | 12:00:00 AM | 01:00:00 AM | 03:00:00 AM | 07:00:00 |
11:59:59 PM (Sat.) | 12:59:59 AM | 01:59:59 AM | 03:59:59 AM | 07:59:59 |
12:00:00 AM | 01:00:00 AM | 03:00:00 AM | 04:00:00 AM | 08:00:00 |
12:59:59 AM | 01:59:59 AM | 03:59:59 AM | 04:59:59 AM | 08:59:59 |
01:00:00 AM | 03:00:00 AM | 04:00:00 AM | 05:00:00 AM | 09:00:00 |
01:59:59 AM | 03:59:59 AM | 04:59:59 AM | 05:59:59 AM | 09:59:59 |
03:00:00 AM | 04:00:00 AM | 05:00:00 AM | 06:00:00 AM | 10:00:00 |
As the first Sunday in November is upon us - this year it will be 03 November 2013 - the reverse occurs.
Pacific Time | Mountain Time | Central Time | Eastern Time | UTC |
10:59:59 PM (Sat.) | 11:59:59 PM (Sat.) | 12:59:59 AM | 01:59:59 AM | 05:59:59 |
11:00:00 PM (Sat.) | 12:00:00 AM | 01:00:00 AM | 01:00:00 AM | 06:00:00 |
11:59:59 PM (Sat.) | 12:59:59 AM | 01:59:59 AM | 01:59:59 AM | 06:59:59 |
12:00:00 AM | 01:00:00 AM | 01:00:00 AM | 02:00:00 AM | 07:00:00 |
12:59:59 AM | 01:59:59 AM | 01:59:59 AM | 02:59:59 AM | 07:59:59 |
01:00:00 AM | 01:00:00 AM | 02:00:00 AM | 03:00:00 AM | 08:00:00 |
01:59:59 AM | 01:59:59 AM | 02:59:59 AM | 03:59:59 AM | 08:59:59 |
01:00:00 AM | 02:00:00 AM | 03:00:00 AM | 04:00:00 AM | 09:00:00 |
For those of you noticing, that means the spring change day has only 23 hours, while the fall change day has 25 hours. Believe me, when you work overnight shifts like I do, it makes a difference!
Any questions? Anyone wish to add info about how time changes occur where you live?