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January 1, 2008 / vivator

Happy New Gregorian Year 2008!

Today we celebrate the first day of 2008 according to Gregorian calendar.  The calendar got its name from Pope Gregory XIII, who reigned from 14 May 1572 to 10 April 1585.  He introduced the new calendar on February 24, 1582 to replace the calendar being used since the time of Julius Caesar (c. 46 BC), the emperor of Rome – hence it bears his name, Julian calendar.

Why there was a need to change calendar?  Both Gregorian and Julian calendars are solar calendars, i.e. they are based on the time the earth takes to make full revolution around the sun.  We know that it takes the earth 365.242199 days to do it.  In Julian calendar one year is counted as 365.25 days – every four year we have leap year by adding one day extra to otherwise 365-day year.  This makes Julian calendar 0.007801 days (or around eleven minutes) too slow every year.  At first it looks like small and negligible number but for every 128.1887 year, Julian calendar is one full day behind – after 1600 years the error accumulates to more than 10 days. This posed a problem since the date of Easter is linked to the first day of spring – with Julian calendar it, then, came too early in sixteenth century.   At the advice of his astronomer Pope Gregory XIII cut ten days from Julian calendar – the next day after Oct 4, 1582 was Oct 15, 1582.  The new calendar still has leap year for every four year except for years ending with “00”, unless they are divisible by 400.  Thus 1700, 1800, 1900 were not leap years, but 1600 and 2000 were.  For every 400 years Gregorian calendar has 303 years with 365 days and 97 years with 366 days.  This works out into 365.2425-day year, close to 365.242199 days of the true year. It still has error – it is too slow by 0.000301 days per year (around 26 seconds).  It will take more than 3,300 years to make Gregorian calendar one full day behind. Compared to Julian calendar Gregorian calendar is now thirteen days ahead (ten days cut in 1582 plus three non leap years in 1700, 1800 and 1900).  

The new calendar was first accepted by European countries with Catholic majority. It was adopted in the same year in Italy, Luxembourg, Portugal, Poland, Spain and France. Germany (Catholic part), Belgium and the Netherlands followed in 1584.  Denmark and part of Germany with Protestant majority adopted it in 1704.  It took 170 years, in 1752, for Great Britain and its colonies to finally switch to Gregorian calendar.  Most eastern European countries, with Eastern Orthodox Christian majority, switched to new calendar in 20th century.  Greece was the last European country to adopt Gregorian calendar in 1923.  Russia or then, Soviet Union, did it in 1918. Some Eastern Orthodox churches still uses Julian calendar as Church calendar until today – this explains why they celebrate Christmas on different day. Their next Christmas is 7 January 2008, according to Gregorian calendar (it is 25 December 2007 according to Julian calendar).

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