Terms: The abbreviation A.D. stands for Anno Domini (Latin) - "in the year of the Lord", meaning the year(s) since Christ's birth. It wasn't adopted until around 386 A.D. when a Catholic monk decided to find out how many years had past since Christ's birth. Sadly he was 7 years off. So instead of Christ being born in 1 A.D. (because there is no 0 A.D.), Jesus was actually born in 7 B.C. What I mean is if the monk had found the correct year, this year wouldn't have been 2003, but 2010. Due to the fact that there is so much hatred towards religions in today's society the term B.C. (Before Christ) has changed to B.C.E. - Before the Common Era. For the same reason A.D. is moving towards A.C.E. - After the Common Era. Molad means "new moon" or more accurately, "birth of moon". A.M. is "Anno Mundi" which means "year of the world" that is the year of creation. (ante) is before the calendar was implemented, (post) is after the expiration of the calendar. For example, before the Gregorian calendar was the Julian calendar. Before the Julian calendar you have the Roman calendar and various other cultures, but for this program that would be the Jewish calendar. Tidbit: Most U.S. official certificates, decrees, laws, etc. must spell out the meaning of A.D. but in English to "in the year of the Lord". So 12-16-2002 (mm-dd-yyyy) on a U.S. certificate would be "This, the Sixteenth day of December, in the year of the Lord Two Thousand and Two, ..."

Gregorian Calendar Stats: The actual repeatable cycle of the Gregorian calendar is 400 gregorian years. Hence, the average gregorian year is 365.2425 days long. That means that the Gregorian calendar is slower than the mean tropical solar year by about 3 days in every 10,000 years. For more detailed information, go to this page.

Jewish Calendar Stats:

The accuracy of the Hebrew calendar is fixed by the value of the mean lunation period coupled to the 19 year cycle of 235 lunar months. This is called a molad (new moon), which is exactly 29 days, 12 hours and 793 halakim (parts), or 3 1\3 seconds. One hour is broken into 1080 halakim. This means that the computations for a date are so accurate that any mean lunar conjunction can be found within 1 day in 14,000 years. That leads to an average Hebrew year length of 365.2468 days. The mean tropical solar year is about 365.2422 days. Hence, the average Hebrew year is slower than the average solar year by about one day in every 216 years. That means that today, we celebrate the holidays, on average about 8 days later than did our ancestors in 359 AD at the time that the fixed calendar rules were published. This makes the Hebrew calendar the most accurate in the world.

According to Jewish tradition, the year 1 of the Jewish calendar was the time of "waste and void" referred to in Genesis 1:1. Nothing was yet created, and only a virtual clock started to tick on the first day of that year, heard, as it were, only by the Creator, on the first day of the week (Sunday) the 24th of Elul, (22 August 3760 B.C. in the Gregorian calendar). He said "Let there be light", and He finished the following Sabbath (Saturday) which is the first day of Tishri, year 2. All Hebrew days begin at 18:00 hours which corresponds to hour zero of the Hebrew calendar's day. The first day of the Hebrew calendar is Sunday at 11:20:11 P.M. This would actually be Monday, because the Jewish day is considered to begin at sunset. Since sunset varies, the day is assumed to begin at 6:00 P.M. for calendar calculation purposes. So, the first molad was 5 hours 793 halakim after the start of Tishri 1, 0001 (which was Monday September 7, 3761 B.C. by the Gregorian calendar).

Julian Calendar Stats:

The old Roman calendar was very complicated and required a group of men, known as the pontiffs, to decide when days should be added or removed to keep the calendar in track with the seasons. This made planning ahead difficult and the pontiffs were open to bribery in order to prolong the term of elected officials or hasten elections. In order to avoid these problems Julius Caesar abolished the use of the lunar year and the intercalary month, and regulated the civil year entirely by the sun. With the advice and assistance of Sosigenes, he fixed the mean length of the year at 365 1/4 days, and decreed that every fourth year should have 366 days, the other years having each 365. In order to restore the vernal equinox to the 25th of March, the place it occupied in the time of Numa, he ordered two extraordinary months to be inserted between November and December in the current year, the first to consist of thirty three, and the second of thirty-four days. The intercalary month of twenty-three days fell into the year of course, so that the ancient year of 355 days received an augmentation of ninety days; and the year on that occasion contained in all 445 days. This was called the last year of confusion. The first Julian year commenced with the 1st of January of the 46th before the birth of Christ, and the 708th from the foundation of the city.

In the distribution of the days through the several months, Caesar adopted a simpler and more commodious arrangement than that which has since prevailed. He had ordered that the first, third, fifth, seventh, ninth, and eleventh months, that is January, March, May, July, September and November, should have each thirty-one days, and the other months thirty, excepting February, which in common years should have only twenty-nine days, but every fourth year thirty days. This order was interrupted in 8 B.C. to gratify the vanity of Augustus, by giving the month bearing his name as many days as July, which was re-named after the first Caesar during 44 B.C. A day was accordingly taken from February and given to August; and in order that three months of thirty-one days might not come together, September and November were reduced to thirty days, and thirty-one given to October and December.

The additional day which occurred every fourth year was given to February, as being the shortest month, and was inserted in the calendar between the 24th and 25th day. February having then twenty-nine days, the 25th was the 6th of the calends of March, sexto calendas; the preceding, which was the additional or intercalary day, was called bis-sexto calendas,--hence the term bissextile, which is still employed to distinguish the year of 366 days. The English denomination of leap year would have been more appropriate if that year had differed from common years in defect, and contained only 364 days. In the modern calendar the intercalary day is still added to February, not, however, between the 24th and 25th, but as the 29th.

In the Julian calendar, the tropical year is approximated as 365 1/4 days = 365.25 days. This gives an error of 1 day in approximately 128 years. The approximation 365 1/4 is achieved by having 1 leap year every 4 years. The rule is that every year divisible by 4 is a leap year.

Comments:

It does not seem to matter how you look at it, figuring out the right date isn't easy. Something to keep in mind though is that the moon has been moving away from the earth at about 3.5 cm a year. So the lunar cycle has grown longer over the years. Not by much, but enough if you wish to be accurate. Twice in the 1990's that I know of, December 31st has been lengthened by one second. Even with atomic clocks, no one seems to know what time it is, and that we never seem to have enough of it. :)


Launch Calendar onverter here.