Leap year

Calendar had historically the purpose to let the beginning of the seasons fall year by year on the same date in order to be able to determine the time for example of celebrations or recurring events. tropical year, thus the period between two Spring-day-and-night-same, lasts however about 365 and somewhat less than 6 hours (365d 5:48:45.98, not constantly!), so that a simple allocation, which gives the same number of days to each year, is impossible, without itself at the same time the beginning that Seasons shifts. In the calendars of the different cultures there are therefore methods, in order to approximate the respective duration of the yearly the tropical year.

The beginning of the seasons can be held for example on the same date, if in suitable distances Leap year, one year with an additional day, that Intercalary day, one inserts. A simple method is to raise each year with one smoothly by 4 divisible year to the leap year. Thus it became in imported, in which February has 29 instead of 28 days. More exact calendars bring the tropical year closer better on: Since somewhat less than six hours per year are to be adjusted, (Julian ones) the intercalary day falls sometimes out (like z. B. in the year 1900 in the Gregorian calendar).

1 Julian calendar
2 Gregorian calendar
3 Orthodox church calendars
4 French revolution calendar
5 Jewish calendar
6 Islamic calendar
7 Chinese calendar
8 Aztec calendar
9 Atomic time
10 Web on the left of

Julian calendar

46 v. Chr. used the Romans a calendar with twelve moon months with alternating 29 each and/or. 30 days, together 354 days. Because straight numbers brought however misfortune, the Romans struck still another one day drauf. But nevertheless were to the sun year still more than ten days too few. First distributed these ten days on the different months, on now 30 and/or. 31 days increased. Only the then last month February went out as a misfortune month empty and remained thus with 29 and/or in the leap year at that time at 30 days. The myth that February lost one day, because emperors in August as monthly designation to perpetuate itself wanted and February still another one day took away, since August like the July, which should have month of its predecessor Caesar, 31 days, and because a straight number also misfortune brought, becomes in the article the month contradicted. But the Romans had a tiny, but on the centuries seen, effective inaccuracy to leave. 11 minutes and 14 seconds per year the then Julian year shot beyond the goal. Every 128 years one leap year was therefore begun too much.

Gregorian calendar

Of Pope became therefore 1582 the following regulation imported ():

By 4 divisible years leap years are smooth.
Smoothly by 100 divisible years are however none Leap years.
Smoothly by 400 divisible years are however again leap years.

Like that those are for example Saekularjahre 1800, 1900 and 2100 no leap years, the Saekularjahre 2000 and 2400 however already. Thus the Gregorian year takes 365.2425 days, and is more exact than the Julian year.

Since that First council of Nicaea in the year 325, with that that Spring beginning on that 21. March , amounted to the accumulated difference was specified already 10 days, and so Gregor left on that 4. October equal that 15. October 1582 follow, in order to adjust this time.

Not in all countries this conversion took place on the same day. There were special difficulties in Sweden, where in the year 1712 two Intercalary days were inserted and thus this year one 30. February had.

Quite unusually and little admits is the fact, that not the 29. February that Intercalary day the Gregorian calendar is. Rather becomes the 24. February doubles: the 24. and the 25. February fall after Roman counting method, also during the introduction of the Gregorian calendar was still usual, on the same date. In the common year is called the 24. February "A. D. VI Kal. Mart."(sixth day before beginning of March); the double day in the leap year is called likewise. There this sixth (lat. "one counts doubly sextus") ("to"), leap year is called and/or. day "bissextilis" (Latin), "bissextile" (english), "bisestile" (Italian) etc.. After today's counting shift the 24. and the further days in February around one day; Meaning has this today still in the catholic church with the counting of the church conferences: church holidays and also the name days are affected by this regulation.

Orthodox church calendars

The Gregorian year is approximately 27 seconds too long. As result the Gregorian calendar limps after 1.600 years around a half day afterwards. Therefore the griechisch-orthodox church suggested a somewhat more complicated switching rule: From the Gregorian calendar the centuries are deviating leap year only if they result in the remainder of 2 or 6 divided by 9. Thus the year 2800 would not be a leap year, but only the year 2900. The deviation to Sun year amounts to with orthodox church calendars only scarcely 3 seconds.

French revolution calendar

In the time, in that that French revolution calendars Validity had, was the years 3, 7 and 11 leap years.

The original regulation of the calendar was that the first day each yearly on the autumnTag-und-Nacht-Gleiche falls and each fourth year one leap year to be is. These demands contradict themselves however, and so struck Charles Rommes, the author of the calendar system, the Gregorian calendar similar a regulation forwards. It encountered however for political reasons thereby resistance. The discussions were however obsolet by the short validity of the revolution calendar.

Jewish calendar

In Jewish calendar, one after that Moon aligned calendar, which is adapted to the sun year by complicated regulations, becomes in all years, which during a division by 19 a remainder inserted of 0, 3, 6, 8, 11, 14, or 17 to have, one switching month. It becomes as Adar II designated.

Islamic calendar

In Islamic calendar the determination of one leap year is extremely difficult. After a common system, among other things in Emacs , is every year, those is used with a division by 30 a remainder of 2, 5, 7, 10, 13, 16, 18, 21, 24, 26, or 29 to have, leap years.

After this system have in the Islamic calendar all even-numbered months 30 days and all odd-number months 29 days. In leap years the last odd-number month one day is added, so that it has then 30 days.

Chinese calendar

Leap years in the traditional, lunisolaren Chinese calendar have 13 months instead of the usual twelve; with 383, 384 or 385 days instead of 353, 354 or 355 days in normal years.

Among the computation one ranks the amount of that Neumonde between the elften month of a yearly (the month that Winter sun turn) and the elften month of the following yearly. If 13 neumonde fall into this period, then one switching month is inserted. The first month, none zhong qì , receives the same number contains as the previous month with an additive as a switching month.

Aztec calendar

In Aztec calendar at the end of each 52-Jahres-Zyklus 13 days are switched on. From it average yearly length of 365 days and 6 hours results. That deviates from the tropical year more than 11 minutes. The accuracy of this leap year method is comparable with the Julian calendar.

Atomic time

Today, in the age that Atomic time measurement, occasionally one must Switching second are inserted, at the time that middle sonnenzeit to adapt.