About Time
Digest from Of Time, Space and Other Things
The lunar month is roughly equal to 29.5days. More exactly,it is equal to 29 days, 12hours,44minutes,2.8seconds,or 29.5306days.
The lunar year built up out of twelve 29.5-day months is 354days long,,whereas twelve lunar months are actually 354.37days long.
Now it so happens that 30 true lunar years come out to be almost exactly an even number of days--10,631.016.Thirty year built up out of 29.5-day months come to 10,620dyas--just 11days short of keeping time with the Moon.For that reason,the Mohammedans scatter 11 days through the 30 years.
The Sun makes its complete cycle about the zodiac in roughly 365 days, so that the lunar year is about 11days shorter that the season-cycle,or "solar year".Three lunar years fall 33 days,or a little more than a full month behind the season-cycle.
19 solar years contain just about 235 lunar months...The Babylonians added that 7-month discrepancy through 19-year cycle...Each cycle had twelve 12-month years and seven 13-month years.
The solar year,however, is not exactly 365 days long...is about 365.25 days long.By 46 BC,the Roman calendar was 80 days behind the Sun...Julian Caesar let 46 BC continue for 445 days so that it was later known as "The Year of Confusion"...In order to take care of that extra 1/4 day, Caesar and Sosigenes established every fourth year with a length of 366 days. It is called Julian year.
The 365-day year is just 52 weeks and 1 day long. If a 366-day year is involved,and if February 6 is on Tues day that year,it is on Thursday the year after.It is for that reason that the 366-day year is called "leap year"and February 29 is "leap day".