why do the seasons not begin on the same day?

Answer 1

since the earth orbit is elliptical, there are times when the earth is closer to the sun then other times. this doesn't make the seasons but it does directly affect how fast the earth is moving around the sun. when the earth is closest to the sun (winter in northern hemisphere) the earth is revolving around the sun faster. and when the earth is furthest from the sun (summer in northern hemisphere) the earth is also revolving slowest. spring and fall are about the same. so the winter season needs to be a few days shorter than summer, so that's why they don't all start/stop on the 21st of months

Answer 2

Simple statistical deviation. The weather is a dynamic system and you simply cannot expect the seasons to start and end at the same time every year,

For example, the growing season in cool climates is equated with summer and is the time between the last frost in spring and the first frost in fall. The average dates are known, but the real dates from one year to the next may be anywhere from 2 weeks earlier to 2 weeks later, in either case.

Answer 3

If you're asking about the official "first day of spring", "first day of summer", etc., it's because there aren't always the same number of days in a year.

As the Earth goes around the sun, a "year" is defined as the time it takes for one complete orbit. In terms of days (as we experience them here on Earth), that comes out to about 365 days, 5 hours, forty-some minutes and an odd number of seconds. We add one extra day every four years, which still leaves us a few minutes off, so we have to leave off the extra day in years which end in "00" (still not quite exact), so we have to adjust again ...

Anyway ... since the days in a "year" aren't exact, there are slight shifts in the calendar from one year to the next. Hope this isn't too confusing.

Answer 4

Firstly,we are adding one day for every four years(leap year)and secondly we are polluting the atmosphere by many ways and this pollution level increases every year.This is the main reason for global warming.Finally, declining forests(due to human activities) affect the weather globally.These are the main reasons for the late or earlier beginning of the seasons.

Answer 5

There's the eccentricity of the earth's orbit, as brandon mentioned. There's also the fact that different months have different lengths, and for year-to-year variation it's mostly the leap year. Over decades to centuries, the earth's axis precesses and the plane of the ecliptic changes.

Answer 6

They don't happen on the same day, if you're referring to monday - friday. Look again at the calender date they begin.