Today is the 31st day of the month, and you don't get so many of those.
30ths occur in everything that isn't February.
29ths are slightly more popular than that.
28ths and below come up all the time.
But 31sts, not so many.
Hebrew months only ever go up to 30. Chinese months only ever go up to 30. Islamic months only ever go up to 30.
That's because these are lunar-based calendars and the moon goes round the earth every 29½ days.
Our Roman calendar ignores the moon and matches with the solar year instead.
365÷12=30½, so months tend to have 30 or 31 days.
Before Julius Caesar only four months had 31 days - March, May, July and October. Julius Caesar added two days to January, Sextilis (August) and December, also making 31.
(April, June, September, and November each got one extra day, making 30).
J
F
M
A
M
J
J
A
S
O
N
D
31
28/9
31
30
31
30
31
31
30
31
30
31
Seven months have 31sts and five don't.
We sometimes go nearly nine weeks without a 31st.
There are two occasions when two consecutive months have 31 days: December/January and July/August.
Every year has seven 31sts, that's 1.9% of the total number of days.
In leap years it's 1.91%, in non leap-years it's 1.92%.
(overall it's 1.9165%)
You have a 1 in 52 chance of being born on the 31st.
You have a 1 in 33 chance of being born on the 30th.
You have a 1 in 32 chance of being born on the 29th.
For the other days of the month it's a 1 in 30 chance.
Less happens on the 31st than on other days of the month.
No UK Prime Minister has been born on the 31st.
No British monarch has been born on the 31st.
Only Henry V died on the 31st (in August 1422).
No US President has been born on the 31st.
The Oscars have only once been presented on the 31st (and only because they were delayed by a day by the shoooting of Ronald Reagan).
Only 6 tube stations were opened on the 31st (but 18 on the 30th and 38 on the 1st).
The five non-existent 31sts are February 31st, April 31st, June 31st, September 31st and November 31st.
Don't they look wrong?
My nephew was born on March 31st.
He's never 'something and a half' years old because there's no September 31st.
This table shows months and the month six months later.
J
F
M
A
M
J
J
A
S
O
N
D
31
28/9
31
30
31
30
31
31
30
31
30
31
J
A
S
O
N
D
J
F
M
A
M
J
31
31
30
31
30
31
31
28/9
31
30
31
30
The only 31sts with a 'something and a half' birthday are January 31st and July 31st.
If you were born on January 31st, happy 'something and a half'th birthday!
