Originally Posted by cave76
O.K.--- then why not have it all year round?
long shaggy dog story follows.
"standard time" is based on the solar day. and, although on a given longtitude (the east-west bit) the sun rises/sets at different "clock" times depending on latitude (the north-south bit) - up to the extremes of the polar regions where the sun never sets/never rises comma by season.
"clock time" is however not established by sunrise/sunset - because that varies by latitude - but rather by the "time" when the sun is highest in the sky.
"noon" - 12PM - 1200, pick a notational convention.... the instant the sun is highest in the sky, regardless of latitude, is the same. meaning that "clock time" is not 'established' by sunrise/sunset, but rather when "noon" happens.
so comma comma, the earth rotates once per day, which is defined as 24 hours (why 24?....) 360 degrees around the earth, divided by 24,,, for every 15 degrees of longitude you travel away from the "Prime Meridian" - which is by convention defined to be Greenwich, UK - "noon" occurs one hour sooner - to the east - or one hour later - to the west.
since the sun's highest point in the sky establishes noon, 8AM happens at 4*60=240 minutes before noon. when the sun rises plays no part.
in an agrarian society, nobody gave a hoot. you got up with the sun and quit when it got dark. and what you did when on your farm was unaffected by any external influences.
This “works” until "civilization" occurs - that means that whole groups of people need to 'cooperate' in some fashion - and cooperating on a 'time schedule' had positive effects vs. "I'll be there when I get around to it." Civilization leads to urbanization, enter the industrial age, creates a huge need for ‘doing things on a time table.
So if the human needs six hours of “sleep” per day, that leaves the human with 18 hours of ‘doing’ something else – and when ‘something else’ was not playing video games, the question of ‘is it dark yet?” comes into play.
(again depending on latitude, but for mid-Atlantic / mid-Mediterranean….) the shortest day (the December winter solstice) is roughly 9 hours, the longest day (June – the summer solstice) 15 hours.
So in the winter, accommodating 18 hours of human activity to occur only during daylight hours is not going to work any which way.
In the summer one can artificially “start the day earlier” so that there is more daylight left at the end of the day. Which is not important if the ‘after hours activity’ is video games and internet forums – but there is a measurable portion of the population who do have other things to do. For them, they still get up with the sun. what “time” is indicated on the watch is actually of no importance.
So, as you can conclude, with a (shortest) day length of 9.5 hours, calculating from noon backwards, sun light appears at 1200-4.5 hours = 0730 by the solar clock.
However at the longest day of 15 hours, sunlight appears at 1200-7.5 hours=0430 by the solar clock. So iffin’ the human spends 0430 to 0700 sleeping abed, the civilized/urbanized human has “wasted” 2.5 hours of daylight. Explains the “savings” part of “Daylight Savings Time”
Could daylight savings time be used “year round?” yes.
Benefit would be:________
Keep in mind the whole kit and caboodle is based on “conventions” – not only the 24 hours/per + 60 minutes/hour thing, but stuff like “the work day.” In USA eight hours is the norm – 40 hours / week. This is not the case in multiple many European countries. China is a whole ‘nother issue.
And keep in mind the execution/implementation of Daylight Savings Time is done at the whim and idiotic rationale of politicians / governments. If you google the history of DST in the USA you’ll find it changes, right regular. Do you think the orbit of the earth or the tilt of the earth’s axis has changed? No, some “think tank” comes up with mysterious “benefits” which requires a “change”
And some local government have opted out of DST – the whole state of Arizona if memory serves; plus quite a number of cites/communities/counties/whatever in the mid-west.
There’s more! In the 70’s-80-90’s when I had a lot of European business dealings, the USA, continental Europe and UK all went on and/or off daylight savings time on different dates. Keeping track of “are they in the office yet / still?” was a real pita.