LAST EDITED ON Aug-20-03 AT 09:50 PM (EST)
 
This is not correct, sir. We know the solar year more accurately than anybody else in history. The calendar year in a particular time zone must start and end at midnight, i.e., the calendar year must have an integer number of days. We can always skip a leap year if the calendar falls out of the step with the solar year by more than, say, 0.5 of a day. This flexibility allows the calendar to be in step with the Sun ± 0.5 day and you cannot do better than that.

Babylonian calendar was a kind of mix between solar and lunar calendars. It was based on the accidental fact that 235 lunar months (235·29.5306 days = 6939.691 days) is approximately equal to 19 solar years (19·365.2422 = 6939.602 days). This calendar lost about 0.089·100/19 = 0.47 days/century to the solar century, which is less than the Julian calendar (0.78 days/century) but more than the Gregorian calendar (0.03 days/century). Moreover, the length of year was jumping around in a fixed pattern during this 19-year cycle, because 1 lunar month had to be added to 7 out of the 19 years. The calendar was periodicaly gaining on and falling behind the Sun and it was never more than about 15 days (half a month) out of step with the Sun.

Moslem calendar, on the other hand, is strictly a lunar calendar. It is based on the accidental fact that 30 lunar years (12 lunar month each) almost exactly equal to an integer number of days: 30·12·29.5306 = 10631.016 days. Compare this with 30 lunar calendar years, where the length of a calendar month alternates between 29 and 30 days, for 29.5 days on the average. 30 lunar calendar years equal to 30·12·29.5 = 10620 days, which is just 11 days short of the 30 true lunar years. Again, these 11 days are scattered through the 30 lunar calendar years in a fixed pattern. The calendar gains 0.016·100/30 = 0.053 days to a lunar century (approximately 97 solar years). The Gregorian calendar with a loss of 0.03 days/century is still better than that.