eli5: Why did we design the months in such a way that winter is in January, February and December in a given calendar year?

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Idk if this is a stupid question or not lol. Obviously when moving from one year to the next, January is right in front of December, e.g. December 2023 is right behind January 2024, but is there a reason that months were designed so that winter carries on into the next calendar year?

We have 12 months and 4 seasons, so each season perfectly divides into 3 months a season. With that in mind, why didn’t we design the months so that winter is in 3 consecutive months within the same calendar year?

I’m not sure if I’ve articulated what I mean properly, so let me know if further clarification is needed.

In: Planetary Science

12 Answers

Anonymous 0 Comments

Seasons don’t switch precisely at a given date each year. Mother nature doesn’t care about our calendar.

If you moved things such that winter was reliably no longer split by the year boundary, then that’d just mean that autumn or spring would get split.

Anonymous 0 Comments

It’s not December. December 21st is the approximate start of winter, and spring starts in March. 70% of December is just late fall, it’s not technically a winter month at least from an astronomical point of view, which is how our calendar is defined.

Anonymous 0 Comments

The Romans used to have a calendar with ten months that started in March and ended in December. Then they just had…”Winter”…which was a more vague period that lasted until they were ready for March again.

In time they added two additional months, January and February, although there were *still* different ways of counting how many days were in each month, so they continued to have shorter “Winter” periods before the year started over in March.

The Julian calendar, established by Julius Caesar in 45 BC, firmly established how many days were in each month and moved the start of the year from March to January 1. Most of the months kept their original names, which is why SEPTember and OCTober are now months nine and ten when they sound like they should be seven and eight (because they used to be). Some time after Caesar, the months Quintillus and Sextillus (once months five and six, now seven and eight) were renamed July and August.

The months may once have been aligned with the equinoxes and solstices, but since the length of the year was so strangely variable for such a long time, those fixed points in the earth’s orbit drifted over the calendar toward where they are now. Indeed, that’s why we moved on to the Gregorian calendar…the March equinox was drifting noticeably, making the scheduling of Easter awkward, exposing a long-term flaw in how the Julian calculated leap years. Our current system keeps the equinoxes and solstices in pretty much the same place for many thousands of years. Yes, it would probably make more sense to start the year at one of these points, and we still could (March 21, 2024 could lead into March 22, 2025), but I say that whoever makes that happen has to also go around and change everyone’s computers.

Anonymous 0 Comments

Overall the season cycle starts again after one year, as the earth has then moved a full circle around sun. The calendar was basically built that way, that a calendar year fits to the seasons cycle, so that you get a rough estimation of the typical season for each month.

However it also depens on your geographic position. On the equator you have almost no classical seasons, and on the southern hemisphere the seasons are inverted. So in Australia they have summer in January.

Anonymous 0 Comments

November used to be the 9th month, not the 11th. At least until the romans changed it by adding Jan and Feb.

Anonymous 0 Comments

It’s politics of Ancient Rome leaking out into a modern day.

January 1st is when newly elected Roman Consuls (“President” and “Vice-President” of Rome) took office. Romans held the office of Consul in a high honor, and their names were displayed in all public places together with a calendar tracking their term. For many regular Romans, this was *the* calendar that they see 90% of the time. Even if officially the year started on a different date – average roman didn’t care.

Now, why did Consuls took office in the middle of the winter? Well, historically, they did it on a different days, but Jan 1st is the one that had finally stuck. Consuls were also Commanders-in-Chief – so it make sense to switch office when there is the least military need. Fighting in the winter was extremely dangerous at the time, so most armies stayed put. Old Consuls could bring their army home before Jan 1st, so the new Consuls could take over and drill it until spring.

When Julius Caesar reformed the calendar – he officially confirmed Jan 1st as the start of a year.

Anonymous 0 Comments

Not a historical answer, but I’ve always thought the cycle of the year in the northern hemisphere is a nice analogue for the cycle of the day. The day begins at midnight, and then the sun gradually gets higher in the sky until midday, and then ends again at midnight. The (northern hemisphere) year starts near the winter solstice, the “midnight” of the year, and then we get more and more sun until the midyear summer solstice when it starts to set again.

Fun trivia fact: the Jewish day begins at sundown, and the new year begins close to the fall equinox, the “dusk” of the year.

Anonymous 0 Comments

If you keep moving south your point gets kind of moot and if you move South far enough it gets completely flipped.
Edit: I meant this has a reply to Op. I didn’t mean to reply to your comment

Anonymous 0 Comments

As others have pointed out, Julius Caesar reformed the Roman calendar in 46 BC, and continued the practice of using January 1st.

However, that’s not the end of the story. At the same time, Alexandria and Egypt kept New Year’s day as 29 August. Some areas honored Augustus by using his birthday, 23 September. The Byzantines (Eastern Roman Empire) switched to using 1 September, and some Eastern Orthodox churches used that as the start the liturgical year for a long while. As Rome’s influence waned, everyone started doing their own thing, particular Christian areas. 25 December was popular in Medieval times, or Easter, or other religious events.

Catholic areas in Europe switched to 1 January around the same time as the Gregorian calendar was rolled out in the 16th Century.

Great Britain used Lady Day (The Feast of the Annunciation), 25 March. Except Scotland decided around 1600 to switch to 1 January. Which isn’t confusing at all. If you see old dates shown as something like “14 February 1701/02”, that means it was 1702 in Scotland (New Style), but still 1701 in other parts of Great Britain (Old Style). Even more confusing, the New Year’s celebration became 1 January, for a couple of centuries before it officially changed.

The British, and their colonies, switched to 1 January in 1752 with the “Calendar (New Style) Act of 1750”. The same act switched to the Gregorian calendar. The (at the time) 11-day difference meant that 25 March Julian was 5 April Gregorian. Britain’s tax day continues to be 5 April instead of moving it to 1 January, and other annual and quarterly dues continued in that fashion.

The US does not actually have a calendar law. The founders adopted British common law as written in 1776 unless overridden by an act of Congress.

Eastern Orthodox churches still on the Julian calendar use 1 January, but since there’s a 13-day difference between Julian and Gregorian, it occurs on everyone else’s 14 January.

Anonymous 0 Comments

Did you realise that the seasons change at different points across a hemisphere according to latitude, and is entirely reversed between north and south hemispheres? So we could never line this stuff up