Portal:Organized Labour/February/30
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Febuary the 30thdid happen look at this Why Leap Years Are Used This page provides the history of the leap year and the purpose it serves. February 29, 2008 The year 2008 is a leap year. If you look at a 2008 calendar, you will see that February has five Fridays–the month begins and ends on a Friday. Between the years 1904 and 2096, leap years that share the same day of week for each date repeat only every 28 years. The most recent year in which February comprised five Fridays was in 1980, and the next occurrence will be in 2036. February 29, the leap day, has been associated with age-old traditions, superstitions and folklore. What is a leap year? A leap year is a year in which one extra day has been inserted, or intercalated, at the end of February. A leap year consists of 366 days, whereas other years, called common years, have 365 days. Which years are leap years? In the Gregorian calendar, the calendar used by most modern countries, the following three criteria determine which years will be leap years:
Every year that is divisible by four is a leap year; of those years, if it can be divided by 100, it is NOT a leap year, unless the year is divisible by 400. Then it is a leap year. According to the above criteria, that means that years 1800, 1900, 2100, 2200, 2300 and 2500 are NOT leap years, while year 2000 and 2400 are leap years.
It is interesting to note that 2000 was somewhat special as it was the first instance when the third criterion was used in most parts of the world.
In the Julian calendar–introduced by Julius Caesar in 46 BC and patterned after the Roman calendar–there was only one rule: any year divisible by four would be a leap year. This calendar was used before the Gregorian calendar was adopted.
Why are leap years needed? Leap years are needed to keep our calendar in alignment with the earth's revolutions around the sun. Details
Note: The illustration is not to scale. The vernal equinox is the time when the sun is directly above the Earth's equator, moving from the southern to the northern hemisphere.
The mean time between two successive vernal equinoxes is called a tropical year–also known as a solar year–and is about 365.2422 days long.
Using a calendar with 365 days every year would result in a loss of 0.2422 days, or almost six hours per year. After 100 years, this calendar would be more than 24 days ahead of the season (tropical year), which is not desirable or accurate. It is desirable to align the calendar with the seasons and to make any difference as insignificant as possible.
By adding a leap year approximately every fourth year, the difference between the calendar and the seasons can be reduced significantly, and the calendar will align with the seasons much more accurately.
(The term "day" is used to mean "solar day"–which is the mean time between two transits of the sun across the meridian of the observer.)
Is there a perfect calendar? No calendars used today are perfect; they are off by seconds, minutes, hours or days every year. To make a calendar more accurate, new leap year rules have to be introduced to the Gregorian calendar, complicating the calculation of the calendar even more. It will, however, need some modifications in a few thousand years. As for the tropical year, it is approximately 365.242199 days, but varies from year to year because of the influence of other planets.
Name of calendar When introduced Average year Approximate error introduced Gregorian calendar AD 1582 365.2425 days 27 seconds (1 day every 3,236 years) Julian calendar 45 BC 365.25 days 11 minutes (1 day every 128 years) 365-day calendar - 365 days 6 hours (1 day every 4 years) Lunar calendar ancient 12-13 moon-months variable
A calendar similar to the Julian calendar, with every fourth year earmarked as a leap year, was first introduced by King Ptolemy III of Egypt in 238 BC.
In ancient times, it was customary to have lunar (moon) calendars, with 12 and/or 13 months every year. To align the calendar with the seasons, the 13th month was inserted as a "leap month" every two or three years. Many countries, especially in Asia still use such calendars. Read more about Leap Year in Other Calendars.
Note: Many other calendars have been and still are used throughout the world.
Why the change from the Julian to the Gregorian calendar? The Julian calendar introduced too many leap days, thus increasing the number of days between the vernal equinox of March 21, its scheduled date as noted in AD 325 during the Council of Nicaea. The introduction of the Gregorian calendar allowed for realignment with the equinox; however, a number of days had to be dropped when the change was made. Click on any one of the year links below for a better explanation of the calendars and the days that were dropped in order to make the switch to the Gregorian calendar.
The Gregorian calendar was first adopted in Italy, Poland, Portugal and Spain in 1582. This was done by dropping 10 days in October of that year. .In Great Britain (and America), the Gregorian calendar would not be adopted until much later, in September 1752; 11 days were dropped. Sweden (and Finland) had a "double" leap year in 1712. Two days were added to February–creating a date of February 30, 1712. (This was done because the leap year in 1700 was dropped and Sweden's calendar was not synchronized with any other calendar. By adding an extra day in 1712, they were back on the Julian calendar.) Read more about February 30 .The Julian calendar is currently (between the years 1901 and 2099) 13 days ahead of the Gregorian calendar (because too many leap years were added). Other leap years facts The Gregorian calendar has a 400-year cycle until it repeats the same weekdays for every year–February 29, 2008, is a Friday and February 29, 2408, is a Friday. The Gregorian calendar has 97 leap years during those 400 years. The longest time between two leap years is eight years. The last time that occurred was between 1896 and 1904. The next time will be between 2096 and 2104. Advertising More information About Leap Day – February 29 Leap Day – Famous Birthdays and Events February 30 Was a Real Date Further reading World Events during Leap Year 2008 Anthony – Leap Year Capital of the World Leap Year in Other Calendars Calendar tools Calendar for year 2008 Calendar Generator – Create a calendar for any year Repeating calendars – Which years share the same calendar?
from site http://www.timeanddate.com/date/leapyear.html February 30 was a real date at one point in time in Sweden and the Soviet Union. However, the introduction of this date was temporary. In Sweden, February 30 resulted from an error with calendar conversion in the 18th century. About two centuries later, the Soviet revolutionary calendar featured February 30 as a result of an attempt to cut seven-day weeks into five-day weeks and to introduce 30-day months for every working month.
Swedish national flag ©iStockphoto.com/resonantsSweden’s 30 Days of February In 1700 Sweden, which included Finland at the time, planned to convert from the Julian calendar to the Gregorian calendar. Therefore 1700, which should have been a leap year in the Julian calendar, was not a leap year in Sweden. However, 1704 and 1708 became leap years by error. This left Sweden out of synchronization with both the Julian and the Gregorian calendars, so the country reverted back to the Julian calendar. February 30 1712 came into existence in Sweden when the Julian calendar was restored and two leap days were added that year. Sweden’s final conversion to the Gregorian calendar occurred in 1753, when a 10-day correction was applied so that February 17 became March 1 that year. Not everyone was pleased with the calendar reform. They believed this event stole 11 days of their lives.
The Soviet Revolutionary Calendar February 30 existed from 1930-1931 after the Soviet Union introduced a revolutionary calendar in 1929. This calendar featured five-day weeks, 30-day months for every working month, and the remaining five or six days were “monthless” holidays. The abolition of the seven-day week in favor of a five-day week was intended to improve industrial efficiency by avoiding the regular interruption of a non-working day. However, the Gregorian calendar continued to be used in the Soviet Union during this period. This is confirmed by consulting the successive dates in daily issues of Pravda, the official newspaper of the Communist Party, in which February had 28 days in 1930 and 1931, in accordance with the Gregorian calendar. The Soviet revolutionary calendar was eventually discarded as it was difficult to eliminate the Sunday rest tradition. The original seven-day week was restored in 1940.
Fact or Fiction: The Julian Calendar The 13th century scholar Johannes de Sacrobosco claimed that February had 30 days in leap years between 45 BCE and 8 BCE in the Julian calendar, when February was shortened to give the month of August the same length as the month of July. However, historical evidence relating to the Julian calendar refutes Sacrobosco, who was critical of that particular calendar.
Advertising More information About Leap Day – February 29 Leap Day – Famous Birthdays and Events Why and When Leap Years are Used Further reading Leap Year in Other Calendars World Events during Leap Year 2008 Anthony – Leap Year Capital of the World Calendar tools Calendar for year 2008 Calendar Generator – Create a calendar for any year Repeating calendars – Which years share the same calendar?
