Fall back, Spring ahead, when to use PST vs PDT |
Being today is one of the two days a year in some locales it is necessary to change clocks — computer users probably have this done for them already — I thought it would be interesting to look a bit deeper behind the scenes of Daylight Savings time. via standardtime.com:
The Uniform Time Act of 1966 provided the basic framework for alternating between daylight saving time and standard time, which we now observe in the United States. But Congress can’t seem to resist tinkering with it. For example, in 1973 daylight saving time was observed all year, instead of just the spring and summer. The current system of beginning DST at 2 AM on the first Sunday in April and ending it at 2 AM on the last Sunday in October was not standardized until 1986.
So things have only been this way since 1986? I don’t remember the change in law back then. Also, Daylight Savings Time isn’t observed in some farming areas at all.
Timeanddate.com explains when to use PDT instead of PST:
PST is used during winter in these US states (PDT during summer)
* California
* Idaho - western counties
Benewah, Bonner, Boundary, Clearwater, Kootenai, Latah, Lewis, Nez Perce, Shoshone and north part of Idaho
* Nevada
* Oregon - except most of Malheur county
* Washington
Good thing we only have to think about this a couple times a year. Our alarm clock and my watch are the only time devices needing manual change.
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They’re changing the standard again next year from what I’m told. Extended months.
Comment by darkmoon — October 29, 2006 @ 12:04 pm PST
Time zones are surprisingly tricky. Last year I added a feature to our (server) software product to let users set the time zone. I was surprised to find out that the US actually has 11 time zones. This includes Alaska, Hawaii, and also the multiple configurations of daylight savings time in Indiana. (Indiana contains 4 timezones: eastern and central, and with and without DST).
At the risk of providing too much information, here’s the documentation I wrote about this for our software. Note the reference to the authoritative tz database and Time Zone Converter
[tdavid, please feel free to edit out below if it seems inappropriate or not relevant]
WILL
***
By default, all date and times displayed on Forio Broadcast Professional are based on US Pacific Time. Similarly, all date and times displayed in simulations served by Forio Broadcast Enterprise follow the time zone setting of the physical server.
Any displayed time can be adjusted to a specific time zone by using a date formatting method with the optional time zone argument. This will adjust the time by the correct number of hours taking into account daylight savings time in the new time zone. Note that the start and end date for daylight savings time will vary depending on the location and country.
The names for time zones are based on the standard tz database. More information can be found on the tz web site. Additionally, the Time Zone Converter provides a detailed list of time zone settings per country.
Below are the options for the US time zones. Note that there are a number of different choices due to differences in daylight savings time. (For example, Arizona does not follow standard US daylight savings time).
Time Zone
US/Alaska
US/Aleutian
US/Arizona
US/Central
US/East-Indiana
US/Eastern
US/Hawaii
US/Indiana-Starke
US/Michigan
US/Mountain
US/Pacific
US/Samoa
Finally, the time zone may also be specified as an offset of GMT (Greenwich Mean Time). In such cases the displayed time will not include any adjustments for daylight savings time. For example, the first two time zones below will be 8 hours before GMT. (e.g. Pacific Standard Time), while the third time zone will be one hour after GMT (e.g. Central European Standard Time).
Comment by Will — October 29, 2006 @ 2:48 pm PST
good info, Will, thanks for sharing
Comment by TDavid — October 29, 2006 @ 3:13 pm PST