Christian and jewish dating
Based on moon cycles instead of sun cycles "Leap months" are added to sync up with sun cycles Used to be calculated by observation Calculated mathematically since 4th century Years are numbered from Creation A few years ago, I was in a synagogue, and I overheard one man ask another, "When is Chanukkah this year?" The other man smiled slyly and replied, "Same as always: the 25th of Kislev." This humorous comment makes an important point: the date of Jewish holidays does not change from year to year.
The Jewish calendar is based on three astronomical phenomena: the rotation of the Earth about its axis (a day); the revolution of the moon about the Earth (a month); and the revolution of the Earth about the sun (a year).These three phenomena are independent of each other, so there is no direct correlation between them.On average, the moon revolves around the Earth in about 29½ days.The Earth revolves around the sun in about 365¼ days, that is, about 12.4 lunar months.The civil calendar used by most of the world has abandoned any correlation between the moon cycles and the month, arbitrarily setting the length of months to 28, 30 or 31 days.The Jewish calendar, however, coordinates all three of these astronomical phenomena.
Months are either 29 or 30 days, corresponding to the 29½-day lunar cycle.
Years are either 12 or 13 months, corresponding to the 12.4 month solar cycle.
The lunar month on the Jewish calendar begins when the first sliver of moon becomes visible after the dark of the moon.
In ancient times, the new months used to be determined by observation.
When people observed the new moon, they would notify the Sanhedrin.
When the Sanhedrin heard testimony from two independent, reliable eyewitnesses that the new moon occurred on a certain date, they would declare the rosh chodesh (first of the month) and send out messengers to tell people when the month began.