Month lengths in the Gregorian calendar

[jim mcnamara]

This "rhyme"

Thirty days hath September, April, June, and November, all the rest have thirty one. Except February.

gives number of days in our months.

I encountered that in elementary school. My late wife who was Greek used the knuckle mnemonic, which I like better:
https://en.wikipedia.org/wiki/Knuckle_mnemonic

Does anyone else know of another way to help remember the number of days in a given month?

 

[mfb]

31 days in odd months up to July, in even numbers afterwards. But it's just 7 months (or 5 if you take the shorter months), I simply know them without any mnemonic.

July and August - the two breaking the pattern - both have 31 days because they are named after Roman rulers who couldn't have short months named after them.

 

[fresh_42]

I learned to remember the word apjuseno.

 

[BillTre]

I usually don't remember them, other than the current month.
I look them up (calendar).

 

[Klystron]

This "rhyme"
gives number of days in our months.
I encountered that in elementary school. {snip}
Does anyone else know of another way to help remember the number of days in a given month?

I also learned the number of days in each month using the song mnemonic. Eventually, I just remembered them. February is tricky in that you must compute leap years.

The "day in month" song reminds me of a similar song to learn the letters of the alphabet.
"A B C D efg H-I J-K lmnop. Q R S, T U V. W X, Y & Z"
I once worked in a campus veteran's office with a fellow recovering from moderate brain injuries. When asked to file papers, he faithfully sang the alphabet song under his breath for each paper.

 

[jim mcnamara]

How does apjuseno help with February? febapjuseno?

 

[fresh_42]

How does apjuseno help with February? febapjuseno?

Nobody needs to remember February. It is far too prominent to press it into a rule just for the sake of completeness. The mnemonic with the knuckles is famous here, too, but the question was: "Does anyone else know of another way" and I learned it by ap-ju-se-no. It is ambiguous on "ju", but June comes in by the step 2 rule.

 

[jbriggs444]

I also learned the number of days in each month using the song mnemonic. Eventually, I just remembered them. February is tricky in that you must compute leap years.

The "day in month" song reminds me of a similar song to learn the letters of the alphabet.
"A B C D efg H-I J-K lmnop. Q R S, T U V. W X, Y & Z"
I once worked in a campus veteran's office with a fellow recovering from moderate brain injuries. When asked to file papers, he faithfully sang the alphabet song under his breath for each paper.

Once upon a time I took the opportunity to memorize the alphabet in reverse order, sung to the same tune.

zyx wvut
srqponm
lkj ihgf
edcb a is left
now I know my Z Y X's
Guess I'll have to move to Texas.

 

[Vanadium 50]

Once upon a time I took the opportunity to memorize the alphabet in reverse order, sung to the same tune.

I had a teacher teach sight-singing by giving us Take Me Out To The Ballgame one note off.

It's one two!
Three strikes you're out in!
The old ball game -----!

Much harder to read the ink in that case.

 

[Astronuc]

If only a year was 366 days (30,31 or 30,31 repeated 6 times), or 360 days (12 * 30), instead of ~365.25 days.

https://en.wikipedia.org/wiki/Year#Astronomical_years

Or if only the universe worked in whole numbers.

 

[Vanadium 50]

Just wait about 10 million years and it will all work out.

 

[DrGreg]

If only a year was 366 days (30,31 or 30,31 repeated 6 times), or 360 days (12 * 30), instead of ~365.25 days.

... and the Earth's orbit was circular rather than elliptical.

 

[mfb]

If only a year was 366 days (30,31 or 30,31 repeated 6 times), or 360 days (12 * 30), instead of ~365.25 days.

We could make 30,31 repeated 6 times where the last day of the last month is skipped in 3/4 of the years. The current system is needlessly complicated.

 

[david2]

July and August - the two breaking the pattern - both have 31 days because they are named after Roman rulers who couldn't have short months named after them.

thats absolutely right

and augustus did that by stealing a day from february

 

[256bits]

Change the whole calendar to an 8 day week.
4 weeks/ per month -> 32 days per month -> 11 months like that.
One of the 12 months is 13 and 1/4 days - > 12 days are work days and 1 and 1/4 is a free holiday (2 days on a leap year)
That way a four day work week works perfect - 4 days on, 4 days off, statutory days are carried over to your time off periods. Everyone would love it. And no more rhyme.

 

[betinajessen]

A lunar month is about 29.5 days. If you wish to transition to a solar calendar and maintain the number of months (which the Romans did), then you have no choice but to have different days in the months.
The simplest is symmetric. Six 29 days and six 30 days, which averages out to twelve 29.5 day months. But the Romans didn’t like even number days. So the 30 days became 31 days. And the Roman Republic calendar emerged with seven 29 day months, four 31 day months and one 28 day month. February was unique for other reasons, but for answering this question, it’s moot.

The Republic calendar only had 355 days in a normal year, so they had to add 22 or 23 days every other year to sync it up with the sun. They used this calendar for several hundred years, some say as much as 400 years (450BC to 45BC).

When Caesar made his calendar reform in 45BC, he needed to add ten days to bring the 355 day calendar up to 365 days so he could get rid of the 22/23 day “leap year” and turn it into a one day leap year every four years. So four of the seven 29 day months got one day (apparently the fear of even number days wasn’t an issue in 45 BC), and three of them got 2 days. That brought us to seven 31 day months, four 30 day months, and one 28 day month. That’s what the Julian Calendar has.

As the Gregorian calendar we use today only changed the leap year rule, it inherited all the other month lengths unchanged. And here we are today. Seven 31 day months, four 30 day months, and one 28 day month (where leap year is applied).

 

[betinajessen]

A lunar month is about 29.5 days. If you wish to transition to a solar calendar and maintain the number of months (which the Romans did), then you have no choice but to have different days in the months.
The simplest is symmetric. Six 29 days and six 30 days, which averages out to twelve 29.5 day months. But the Romans didn’t like even number days. So the 30 days became 31 days. And the Roman Republic calendar 2023 emerged with seven 29 day months, four 31 day months and one 28 day month. February was unique for other reasons, but for answering this question, it’s moot.

The Republic calendar only had 355 days in a normal year, so they had to add 22 or 23 days every other year to sync it up with the sun. They used this calendar for several hundred years, some say as much as 400 years (450BC to 45BC).

When Caesar made his calendar reform in 45BC, he needed to add ten days to bring the 355 day calendar up to 365 days so he could get rid of the 22/23 day “leap year” and turn it into a one day leap year every four years. So four of the seven 29 day months got one day (apparently the fear of even number days wasn’t an issue in 45 BC), and three of them got 2 days. That brought us to seven 31 day months, four 30 day months, and one 28 day month. That’s what the Julian Calendar has.

As the Gregorian calendar we use today only changed the leap year rule, it inherited all the other month lengths unchanged. And here we are today. Seven 31 day months, four 30 day months, and one 28 day month (where leap year is applied).

That’s actually a little complicated.

It’s first use was in 1582, but that use was confined to areas in which the Catholic church was dominant. Since it was promulgated by a Catholic pope, Protestant-dominated areas generally wanted nothing to do with it.

Adoption was gradual. For example, Great Britain and its colonies (including its American colonies) didn’t adopt it until 1752, twenty-four years before the American Revolution. All of the American “founding fathers” were born under the old calendar.

The last countries to officially adopt it were Turkey, in 1926, and Saudi Arabia, which only adopted it officially in 2016.

So it depends a lot on where it is you’re talking about.

Most places went through a period where they’d indicate dates with “O.S.” (old style) or “N.S.” (new style) to clarify which calendar they were using.