Daylight Savings or "Summer" time... 

Written by Chuck Maddox  on 24 September, 1999, certain rights reserved.

Last Revised: 16 January, 2005, 16:55 GMT

Definition and Origin:

Daylight Saving, also known as DST or Summertime, is the system of setting clocks one or two hours ahead so that both sunrise and sunset occur at a later hour, producing an additional period of daylight in the evening. In the North Temperate Zone, clocks are usually set ahead one hour in the spring and set back to standard time in the fall. The idea of daylight saving was mentioned in a whimsical essay by Benjamin Franklin titled "An Economical Project for Diminishing the Cost of Light". The essay was first published in the Journal de Paris on 26 April, 1784. Daylight savings was first advocated seriously by a British builder, William Willett (1857-1915), in the pamphlet "Waste of Daylight" (1907).

History:

 

Daylight saving has been used in the United States and in many European countries since World War I, when the system was adopted in order to conserve fuel needed to produce electric power. The idea being that most people would arrive home and with an additional hour of daylight in the evening, they would use fewer resources to produce light. Some localities reverted to standard time after the war, but others retained daylight saving. During World War II, the U.S. Congress passed a law putting the entire country on war time, which set clocks one hour ahead of standard time. War time was also followed in Great Britain where, in an act of one-upmanship, clocks were put ahead still another hour during the summer. In the U.S. during peacetime, daylight saving was a subject of controversy. Railroad, bus, and plane scheduling was so hampered by time inconsistencies among various cities and states that the repercussions are still being felt today.

 

Uniform Time Act:

 

The Uniform Time Act, enacted by the U.S. Congress in 1966, established a system of uniform (within each time zone) daylight saving time throughout the U.S. and its possessions, exempting only those states in which the legislatures voted to keep the entire state on standard time. Under legislation enacted in 1986, daylight saving time begins at 2 a.m. on the first Sunday of April and ends at 2 a.m. on the last Sunday of October. Today approximately 70 countries utilize DST in at least a portion of their country.

 

Observance:

However, a number of places in the US, Canada, Austrailia and other countries elect to not observe DST. For example in the United States, most of Indiana, and all of Arizona, Hawaii, and Puerto Rico do not observe DST. In Canada, Saskatchewan does not observe DST but what they did, sometime during the 1940's, was to permanently change the entire provence from Central time to Mountain time, which has the same effect as having Daylight Savings time year around! (Thanks to W.M. Hanover for pointing this out!) In Australia, Queensland, the Northern Territory and Western Australia do not participate in Daylight Saving. This means that Australia has both horizontal and vertical time zones in summer!! This is further complicated by the fact that since Austrailia (and other Southern Hemisphere countries like New Zealand, South Africa, Argentina, etc.) generally observe Daylight Savings opposite of the Northern Hemisphere, in their summer months. Gee, this is complicated! Fortunately, Chrysanthemum Enterprises LLC has a handy chart as to when various countries observe DST.

Commonly, which time a particular locale is observing is denoted by the second character within a abbreviation. For example EST means Eastern Standard Time, EDT means Eastern Daylight Time. ET simply means Eastern Time and varies at different times of the year. Here is a page with more information on abbreviations.

Why this page?

My interest in knowing when various cities around the world observed DST started when I purchased a Citizen NaviHawk World Time Chronograph while in Munich, Germany on business in 1995. Unfortunately, the instruction manual that came with the watch did not shed any light on the subject. So any setting of the summertime functions involved a substancial amount of guesswork. Fortunately, Citizen has recently started selling a new model of the NaviHawk outside of the United States with a manual that has a handy time chart for time differences between the cities on the watch and UTC (or GMT) time. Craig Joseph Poff wrote and posted a well written review of the new model Citizen "Navihawk 3" on TimeZone which mentioned the existance of this chart. I emailed Craig and he was kind enough to fax me a copy of the chart which is recreated below:

# ID City/TimeZone Diff. DST? Diff 1 UTC Universal Time +/-0 2 LON London +/-0 +1 3 PAR Paris +1 +2 4 ROM Rome +1 +2 5 CAI Cairo +2 +3 6 IST Istanbul +2 +3 7 MOW Moscow +3 +4 8 KWI Kuwait +3 9 DXB Dubai +4 10 KHI Karachi +5 11 DEL New Delhi +5.5 12 DAC Dacca +6 13 BKK Bangkok +7 14 SIN Singapore +8 15 HKG Hong Kong +8 16 PEK Beijing +8 # ID City/TimeZone Diff. DST? Diff		# ID City/Time Zone Diff. DST? Diff 17 TYO Tokyo +9 18 SYD Sydney +10 +11 19 NOU Nournda +11 20 AKL Auckland +12 +13 21 HNL Honolulu -10 22 ANC Anchorage -9 -8 23 LAX Los Angeles -8 -7 24 DEN Denver -7 -6 25 CHI Chicago -6 -5 26 MEX Mexico City -6 27 NYC New York -5 -4 28 YUL Montreal -5 -4 29 CCS Caracas -4 30 RIO Rio de Janeiro -3 -2 31 BUE Buenos Aries -3    # ID City/Time Zone Diff. DST? Diff
Notes: Cities (regions) with Summertime are indicatied by the symbol while cities that do not observe summertime are blank in the DST? and Diff columns. Time difference and summertime for cities are subject to change, this information dates from 1997. It was only after converting the Citizen chart and looking at it that I noticed it seems somewhat backwards to me... As the chart starts at UTC/GMT and proceeds East from there. I think that it might make more sense to have the chart start at the international date line and work it's way west like the sun does when viewed from Earth... Maybe when I have the time to modify it.

Permission is granted for Damon, Derek Ziglar, Ross or RJ to include within the FAQ's they are writing as long as credit (and a link to this article) is given. Permission for personal, educational or non-commercial use is granted. The author retains all other rights not specifically mentioned here... For all other use please contact the author.

Disclaimer: Opinions are my own and knowing me should be taken with a grain or two of salt...

-- Chuck