Winter Time and Summer Time

legendary.xix

Hi, I hope I've the right section to ask this question. If not I do apologise in advance.

In late October, less than 2 months before the winter solstice, the clocks go back one hour.
In late March, more than 3 months after the winter solstice, the clock go forward an hour.

Is these changes to be 2 months before the solstice and 3 months after. One might expect late February to be more appropriate, being 2 months after the winter solstice. Is the earth elliptical path around the sun to do with this. 2 months before does not equate to 2 months afterwards?

auti

Hi, I think the answer to your question is that Daylight Saving Time is a completely arbitrary system that does not correspond at all to the rotation of the earth around the sun. Rather than the time changes being two months before the winter solstice and three months after, the system used in Europe is the last Sunday in October and the last Sunday in March. The idea was introduced in Europe during WW1 to help conserve fuel.

Other parts of the world have completely different systems and change the clocks at different times of the year. Some countries change their clocks by 20/30 minutes rather than one hour. Other parts of the world do not even observe Daylight Saving Time.

Hope this helps.

Muppet Man

And in counties that DO officially observe Daylight Saving Time (DST), there are some areas of that country that dont observe DST. E.g. United States does observe DST, but most of the state of Arizona does NOT observe DST.

Zubeneschamali

There is some effect from the elliptical orbit and tilt of the Earth: mornings don't start getting earlier until 2 weeks after the winter solstice. But the dates chosen are not symmetrical even with that.

Popoutman

The earth's slightly elliptical orbit means that the earth's speed changes along its orbit, going faster when closer to the sun in January and slower when farther from the sun in June. This non-constant speed means that the real sun can either lag behind or be ahead of the average "mean" sun that is used for timekeeping purposes - this mean sun is due south at local noon at Greenwich every day of the year. In Limerick, being nearly 9 degrees west from Greenwich has the mean sun due south at about 12.35 pm.
The difference between the position of the real sun and the mean sun is known as the Equation of Time, and this can be anywhere between about 20 minutes ahead or 15 min behind.

Net effect of the equation of time, being that much west of Greenwich, and that silliness that is DST; the sun is actually due south at nearly 14.00 during July in Limerick.

coylemj

Muppet Man wrote: »

And in counties that DO officially observe Daylight Saving Time (DST), there are some areas of that country that dont observe DST. E.g. United States does observe DST, but most of the state of Arizona does NOT observe DST.

In response to your 'confused' emoticon.....

I asked a colleague from Tucson, Arizona why most of the state does not observe DST. His answer was simple: in the Arizona summer you can do nothing in terms of recreation when the sun is shining because it's so damn hot.

The aim of DST is to maximize daylight hours in the evening so as to extend recreational time for outdoor pursuits. The priority in Arizona is not to extend daylight but to hasten nightfall, that's why they don't put the clocks forward in the Spring.

There is a Mojave (American Indian) reservation in NE Arizona which does observe DST.

Since Indiana decided in 2006 to observe DST, I believe Arizona is now the only state in the Continental (48 states) US which does not observe DST.