This table gives an overview of each calendar and a quick comparison between them. For in depth information about any calendar just click on its name. For an explanation of the data given in any column just click 'Explain' at the top of that column.
This page was updated on Monday 8th January 2001 AD (Gregorian).
Calendar  Start date (in Gregorian) 
No. of days per year 
No. of months per year 
Correction applied 
Astronomical  365.24219 approx 

Aztec Sacred 
260  20 of 13 days  
Aztec Solar 
365  18 of 20 days + 5 days 

Babylonian  365.2467463  12 each of 29 or 30 days 
Intercalary month added every 19 years  
Bahai  21 Mar 1844 AD  365.2425  19 of 19 days and 4 or 5 feast days 
If year is divisible by 4 then it is a leap year. If year is divisible by 100 then it is not a leap year. If year is divisible by 400 then it is a leap year. 
Chinese  2637 BC  353 to 385  12 or 13 of 29 or 30 days 
Intercalary month added according to complicated rules. 
Egyptian  365  12 of 30 days + 5 days 
No correction applied.  
English  Unknown  12  
French Revolutionary 
22 Sept 1792 AD  365.24225  12 of 30 days + 5 or 6 days 
Years 3, 7 & 11 were leap years. Calender abolished in year 14. 
Greek Orthodox 
365.24222  12 in total. 7 x 31, 4 x 30, 1 x 28 or 29 
If year is divisible by 4 then it is a leap year. If year is divisible by 100 then it is not a leap year. If year divided by 900 leaves a remainder of 200 or 600 then it is a leap year. 

Gregorian  In theory  1 Jan 1 AD. In practice. 
365.2425  12 in total. 7 x 31, 4 x 30, 1 x 28 or 29 
If year is divisible by 4 then it is a leap year. If year is divisible by 100 then it is not a leap year. If year is divisible by 400 then it is a leap year. 
Hebrew  3761 BC  354 approx 
12 or 13 each of 29 or 30 days. 
If year divided by 19 leaves a remainder of 0, 3, 6, 8, 11, 14 or 17 then it is a leap year and has 13 months. 
Hebrew Jubilee 
364  12 of 30 days + 1 extra day in each quarter. 
No correction applied.  
Indian  22 Mar 79 AD  365.2425  12 in total 5 x 31 7 x 30 
If year is divisible by 4 then it is a leap year. If year is divisible by 100 then it is not a leap year. If year is divisible by 400 then it is a leap year. 
Islamic (Hijri) 
16 July 622 AD  354.36  12 length variable. 
The calender is based on the first sighting of the moon each month and therefore difficult to predict. 
John Dee  Not adopted 
365.2424  12 in total. 7 x 31, 4 x 30, 1 x 28 or 29 
It is a leap year if the year number modulo 32 is not zero and is divisble by four with no remainder. 
Julian  45 BC  365.25  12 in total. 7 x 31, 4 x 30, 1 x 28 or 29 
If year is divisible by 4 then it is a leap year. 
Lunar  354  12 in total. 6 x 29, 6 x 30 
No correction applied.  
Mayan Sacred 
12 Aug 3113 BC  260  20 of 13 days  No correction applied 
Mayan Solar 
12 Aug 3113 BC  365  18 of 20 days + 5 extra days 
No correction applied 
Nepalese  56 BC  varies  12 of 29 to 32 days  Calculated by astrologers 
Persian  22 Mar 622 AD  365.2422  12 in total 6 x 31, 5 x 30 1 x 29 or 30 
One extra day inserted according to the time of the vernal equinox producing a cycle which lasts 33 years. 
Roman  Approx 750 BC  Standard 355 Ave. 366.25 
12 in total. 1 x 28, 7 x 29, 4 x 31 
An additional month of either 28 or 29 days in alternate years. 