Leap day
29/02/16 03:29
You probably already know this, but just in case, let me refresh your memory. The month of February in our current Gregorian calendar got its name from the month of the same name in the Julian calendar. Its name is fashioned from the Latin term februum, which means purification. The prior Roman lunar calendar contained the purification ritual Februa to be held on the full moon in February, which in a lunar calendar landed on the 15th of the month. The festival was one common to many ancient cultures, one of spring cleaning. It dates back to near the time of the founding of Rome. Later, the festival was merged with Luypercalla, a festival observed from February 13 to 15 to avert evil spirits and purify the city, releasing health and fertility. Unlike other months in the Julian calendar, then, February got its name not from a person, but from a ceremony.
If you take a short trip back in history, under the Roman Emperor Julius Caesar, February was like most of the other months in the calendar. It had 30 days. The Roman scheme of 12 months with 30 or 31 days didn’t quite work out and periodic corrections were necessary in order to sync the calendar with the seasons of the year. In order to make things work out they shortened the month following Julius’ month to 29 days. When Caesar Augustus became emperor, his ego needed expression in the calendar and so that month was named after him and received two extra days, making August equal in the number of days to July. February essentially lost out to the ego of Augustus.
The problem is that no matter how you configure the days, it won’t come out with the seasons in the long run because a complete orbit of the earth around the sun takes 365.2422 days com complete, not 365 days as is the case with the calendar. The Gregorian calendar was created to correct the mistake, and perhaps to exert the control of the Christian church over the secular calendar. At any rate, in Gregory’s calendar an extra day is added to the end of February every four years. The extra day has received the common name of “leap day” and the year in which it occurs is “leap year.”
“Ah!” you say, “but that doesn’t come out even either. It would work if an orbit of the earth were 365.25 days, but it isn’t. It is 365.2422 days!” And you are right. That is why leap year is skipped in three of every four years that is divisible by 100. So the years 1700, 1800 and 1900 were not leap years, but the year 2000 was. In this system, 2100, 2200, and 2300 won’t be leap years, but 2400 will be. So here is the complete rule: There is a leap year every year that is divisible by four, except for years that are both disable by 100 and not divisible by 400.
If you’ve got that, you’ll understand why today is February 29 instead of March 1. At least that is the system most of the world has been using since 1582 when the Gregorian calendar was introduced.
Of course, it still doesn’t synchronize perfectly, so leap seconds are periodically added to years to keep the clocks in line with the sunrise. And then there are additional variations, which require a more major adjustment every 10,000 years. So I’m not exactly sure how the calendar will be aligned after the year 2500.
For what it is worth no human calendar system has been devised that does not require leap years. The modern Iranian calendar is a solar calendar with eight leap days in each 33-year cycle. The Indian National Calendar and the Revised Bangla Calendar of Bangladesh arrange their leap years so that the leap day is always close to February 29 in the Gregorian calendar.
This, of course, brings about the problem of leaplings: the people who are born on February 29. If they only are allowed to celebrate their birthdays in years when there is a leap day, the count of their age is off by a significant factor. And, after all, everyone deserves a birthday every year. So the tradition has been formed that those born before noon on February 29 celebrate their birthdays on February 28 when it is not a leap year and those born after noon celebrate on March 1. I guess those born exactly at noon get to choose, or perhaps they are so rare that they ought to get two days of celebration. After all the chances of having a leap birthday are only on in 1,461. That means there are approximately 4.1 million people alive today with a February 29 birthday. The chances of being born precisely at noon are fairly slim and if you calculate in the chance of survival it comes out to something like 1 in 400,000,000,000 making it likely that there is no one alive today who was born precisely at noon on February 29.
If you are a fan of musicals, you know that Frederic, the key figure in Gilbert & Sullivan’s Pirates of Penzance, was born on February 29. He is due to be released from his apprenticeship with a band of pirates on his 21st birthday. However, because his birthday comes only once every four years, he has to serve an additional 63 years before he is released and can join his love, Mabel. She agrees to wait faithfully until that day and that is sufficient plot for the entire musical.
The tradition is that women are only allowed to propose marriage on Leap Day. Lore reports that there was a law passed in Scotland in 1288 that allowed unmarried women to propose on leap year and subjected a man who refused to a fine. It was said to date all the way back to the 5th Century when St Bridget complained to St Patrick that women had to wait too long for their suitors to propose.
Something tells me that that particular tradition will not last until the next major revamping of the calendar.
At any rate, today is a unique day and a good time to celebrate. Enjoy!
If you take a short trip back in history, under the Roman Emperor Julius Caesar, February was like most of the other months in the calendar. It had 30 days. The Roman scheme of 12 months with 30 or 31 days didn’t quite work out and periodic corrections were necessary in order to sync the calendar with the seasons of the year. In order to make things work out they shortened the month following Julius’ month to 29 days. When Caesar Augustus became emperor, his ego needed expression in the calendar and so that month was named after him and received two extra days, making August equal in the number of days to July. February essentially lost out to the ego of Augustus.
The problem is that no matter how you configure the days, it won’t come out with the seasons in the long run because a complete orbit of the earth around the sun takes 365.2422 days com complete, not 365 days as is the case with the calendar. The Gregorian calendar was created to correct the mistake, and perhaps to exert the control of the Christian church over the secular calendar. At any rate, in Gregory’s calendar an extra day is added to the end of February every four years. The extra day has received the common name of “leap day” and the year in which it occurs is “leap year.”
“Ah!” you say, “but that doesn’t come out even either. It would work if an orbit of the earth were 365.25 days, but it isn’t. It is 365.2422 days!” And you are right. That is why leap year is skipped in three of every four years that is divisible by 100. So the years 1700, 1800 and 1900 were not leap years, but the year 2000 was. In this system, 2100, 2200, and 2300 won’t be leap years, but 2400 will be. So here is the complete rule: There is a leap year every year that is divisible by four, except for years that are both disable by 100 and not divisible by 400.
If you’ve got that, you’ll understand why today is February 29 instead of March 1. At least that is the system most of the world has been using since 1582 when the Gregorian calendar was introduced.
Of course, it still doesn’t synchronize perfectly, so leap seconds are periodically added to years to keep the clocks in line with the sunrise. And then there are additional variations, which require a more major adjustment every 10,000 years. So I’m not exactly sure how the calendar will be aligned after the year 2500.
For what it is worth no human calendar system has been devised that does not require leap years. The modern Iranian calendar is a solar calendar with eight leap days in each 33-year cycle. The Indian National Calendar and the Revised Bangla Calendar of Bangladesh arrange their leap years so that the leap day is always close to February 29 in the Gregorian calendar.
This, of course, brings about the problem of leaplings: the people who are born on February 29. If they only are allowed to celebrate their birthdays in years when there is a leap day, the count of their age is off by a significant factor. And, after all, everyone deserves a birthday every year. So the tradition has been formed that those born before noon on February 29 celebrate their birthdays on February 28 when it is not a leap year and those born after noon celebrate on March 1. I guess those born exactly at noon get to choose, or perhaps they are so rare that they ought to get two days of celebration. After all the chances of having a leap birthday are only on in 1,461. That means there are approximately 4.1 million people alive today with a February 29 birthday. The chances of being born precisely at noon are fairly slim and if you calculate in the chance of survival it comes out to something like 1 in 400,000,000,000 making it likely that there is no one alive today who was born precisely at noon on February 29.
If you are a fan of musicals, you know that Frederic, the key figure in Gilbert & Sullivan’s Pirates of Penzance, was born on February 29. He is due to be released from his apprenticeship with a band of pirates on his 21st birthday. However, because his birthday comes only once every four years, he has to serve an additional 63 years before he is released and can join his love, Mabel. She agrees to wait faithfully until that day and that is sufficient plot for the entire musical.
The tradition is that women are only allowed to propose marriage on Leap Day. Lore reports that there was a law passed in Scotland in 1288 that allowed unmarried women to propose on leap year and subjected a man who refused to a fine. It was said to date all the way back to the 5th Century when St Bridget complained to St Patrick that women had to wait too long for their suitors to propose.
Something tells me that that particular tradition will not last until the next major revamping of the calendar.
At any rate, today is a unique day and a good time to celebrate. Enjoy!