Wouldn't it make more sense to start seasons around the 1st of a month instead of the 21st?

Totally curious here. Why do you give a shit?

Wouldn’t work since the years are 365 and ¼ days long. The season would start on the first of the month one year and change to the leading or following day 2 years (or whatever) later.

I think the first of the month was originally meant to coincide with a new moon cycle. I guess that synchrony has been lost over time.

It does seem to make more sense for a monthly occurrence to be the reason for the monthly date. Equinoxes + solstices only account for four firsts.

I thought the seasons were like this because those dates were the point where the earth is physically in the actual transition around the sun to start the new season.

@Blackberry They are – I assume the OP is asking why we didn’t just call the solstice or equinox the 1st, instead of assigning the 1st to some other schedule, and having the solstices and equinoxes fall where they may.

The seasons are determined by the position of the earth relative to the sun. Whomever set up the Gregorian calendar picked the dates – I do not have a clue why they chose the dates they did.

No. Spring and autumn begin at each equinox, when daylight and darkness are equal because the earth’s equator passes the center of the sun. On this day, the tilt of the earth doesn’t lean either away from or toward to sun. Summer and winter start at a solstice, when the sun is highest or lowest relative to the equator.

Our days begin and end at 12:00 midnight, an arbitrary time that’s meaningless and unrelated to sunset and sunrise. How nice that our seasons are still dictated by nature and the earth’s orbit through the solar system.

@kritiper , It would never be off more than a day or two, just like the seasons always start now between the 20th and the 22nd.

@heartkat, The reason, as I pointed out, was so that Easter would coincide with the start of spring.

@SadieMartinPaul , True but we could have changed the calendar so that these events occur on the first of the month.

To everyone, 9 days were removed from the year 1582 to get the 21st of March to coincide with the start of spring. The calendar went from October 5 one day to October 15 the next day. @johnpowell , If you are going to change the calendar, why not do it to have it actually mean something? It is not like I am up in arms about this, but if you are changing the calendar, make it convenient for something.

@LostInParadise

The equinox’s and solstice’s are not fixed calendar dates. There’s a window of a few days they can fall on from year to year. With your proposal we’d have to adjust the calendar each year.

@LostInParadise – But Easter is on a different date every year, based on the equinox and lunar cycles – they still could have chosen to start some months on the equinox and solstice days when changing the Julian system. I’ve always felt that Winter Solstice should be New Year’s… that would only shift the calendar by ~10 days – so I am basically in agreement with you on this.

Something else to consider. If they were fiddling with the calendar, why not change the number of days in a month to make things uniform. Currently, months alternate between 30 and 31 days except for February and the fact that July and August both have 31 days. A saner system would have odd numbered months with an odd number, 31, of days and even numbered months with 30 days. The only exception would be February, which would ordinarily have 29 days and only have 30 days in a leap year. I am all in favor of shortchanging February for the psychological value. February is the coldest month of the year, so it makes sense to make it shorter.

The current numbering does have one advantage. There is a neat trick devised by the mathematician John Conway for knowing which day of the week a day falls on. The last day of February and Apri 4 (4/4), 6/6, 8/8, 10/10 and 12/12 all fall on the same day of the week. If you know one, you know the rest. There is a set of rules for odd numbered months, but it is not, IMHO, worth remembering. Apart from February, which is a lucky coincidence, it is easy to see why the system works. Because of the usual alternation of 30 and 31 days, the number of days between, for example 4/4 and 6/6 is 30 + 31 + 2 = 63, which is divisible by 7.

@LostInParadise: Wow – and people have told me that I overthink such things… it’s nice to know I’m not the only one – and some actually make a career of it! Though I don’t think I’d have made a good mathematician.

@LostInParadise I forgot to mention that there are 366 days in every leap year, leap years occurring every 4 years, but no leap year at the beginning of each century so there is another item that would mess it up. But even if the days were only off by a day or two, the seasons could not start on the first of the month.
Easter varies because of when Lent ends.

@kritiper – There is a leap year at the beginning of a century if it is divisible by 400 – Y2K was a leap year.

@hearkat See? Too many variables!

@hearkat , I plead guilty to the charge of overthinking, but it can be fun to see how things can be sliced and diced.

@LostInParadise – I agree. I embrace my contemplative nature. But as @kritiper points out, there’s too much variability in some things, so my limited brain eventually gets befuddled and I have to take a mathematician at his/her word that it makes sense.