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I read that our day is not exactly 24 hours long. If it is not then why weather seasons come at the same time (Summer, Winter, Autumn Spring) ? how it is equalized ?

Update: Sorry I could not make it clear. My meaning was if 3.8 seconds are shorter of everyday the how is the calculation made that summer starts in May and winter start december everytime why it does not move further since. How time is neutralized ? I hope you guys understood this time.

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    $\begingroup$ Which weather changes did you have in mind? Did you mean the difference in time we measure and length of day from one solar noon to another? "Day" as a unit of time is by definition 24 hours long. Could you please clarify what you're asking about? There are many factors that are at play here, which ones in particular are you inquiring about? $\endgroup$
    – TildalWave
    Dec 27, 2013 at 9:23

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Our day is 23 hours and 56 minutes long, and slowing by an infinitesimal (but measurable) amount each year due to tidal losses.

Our day has a connection with the weather, in that the sun drives all our weather systems, so heating over each part of the globe happens every day, but aside from that, your question doesn't make much sense.

Weather changes may come at the same time where you live (on a 24 hour cycle) but here in Scotland, we still have low reliability on even a 3 day weather forecast, because the weather systems that impact the UK are so complex as heating from the sun drives various air flows.

After your update, I still cannot understand what you mean. There is slippage in accuracy, but this is counteracted by leap seconds and leap years. It has nothing to do with weather. The shortest and longest days happen when they happen and are measurable. They help us define the year.

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    $\begingroup$ 23h 56m is the sidereal day. The solar day is very close to 24 hours. $\endgroup$
    – Keith Thompson
    Dec 27, 2013 at 21:55
  • $\begingroup$ I meant the seasons (instead of weather) like summer, winter, autumn and spring which comes at the same time(at least in my country) sorry my bad... Yes that's what i wanted to know. Its mean that 24 hours(29th feb) are added to our year after every 4 years. means if everyday is 3:55.91 minutes(235.9084 seconds) shorter then every year is 86106.566 seconds shorter which is approximately equals to 24 hours then how after four years >.< confused $\endgroup$
    – Asadullah Ali
    Dec 31, 2013 at 1:51
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    $\begingroup$ No - that isn't how it works. Humans have chosen seconds, minutes, hours etc., but they don't quite match up to reality. The Earth will happily keep doing it's thing, but every now and then we have to realign our measures. The leap year adjustments do this. $\endgroup$
    – Rory Alsop
    Dec 31, 2013 at 11:45
  • $\begingroup$ The realignment part is what sucks. If the world is revolving around the sun at a steady rate, what is that rate in milliseconds? Milliseconds are the most basic unit used in computer programming; seasons be damned. Myself, I am interested in working out the math as it relates to the leap year. I'm surprised this question is closed. $\endgroup$
    – Joshua Dannemann
    Mar 12, 2016 at 23:02
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    $\begingroup$ Joshua - the question is closed as it doesn't really make sense as it's written. Leap years/leap seconds only exist as a human construct. They aren't real. $\endgroup$
    – Rory Alsop
    Mar 13, 2016 at 8:00
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The length of a solar day is very close to 24 hours. A solar day is the time it takes the Sun to return to the same position in the sky. The exact length varies slightly over the course of the year, because the Earth's orbit around the Sun is not perfectly circular; the tilt of the Earth's axis with respect to its orbit also has an effect. See the linked article for details.

A sidereal day is slightly shorter. It's the time it takes for a distant star to return to the same position in the sky, and it differs from the solar day because the Earth revolves around the Sun as it rotates on its own axis; there is one more sidereal day than solar day each year. A sidereal day is approximately 23 hours, 56 minutes, 4.0916 seconds.

Weather can actually have a minuscule effect on the Earth's rotation, as the mass of the atmosphere is distributed differently. This effect is barely measurable. I don't think that's the kind of "weather changes" you were asking about; can you clarify? Obviously it gets colder at night, and that's controlled by the length of the solar day.

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