Hebrew Month

Hebrew Month

The Hebrew or Jewish calendar (הַלּוּחַ הָעִבְרִי, ha'luach ha'ivri) is a lunisolar calendar used today predominantly for Jewish religious observances. It determines the dates for Jewish holidays and the appropriate public reading of Torah portions, yahrzeits (dates to commemorate the death of a relative), and daily Psalm readings, among many ceremonial uses. In Israel, it is an official calendar for civil purposes and provides a time frame for agriculture. The current year of the Jewish calendar (16 September 2012 to 4 September 2013) is AM 5773.

The Hebrew calendar has evolved over time. For example, until the Tannaitic period (approximately 10–220 CE) the months were set by observation of a new crescent moon, with an additional month added every two or three years to correct for the difference between twelve lunar months and the solar year and, therefore, to keep Passover in the spring. The addition of the extra month was also based on observation of natural events: specifically, the ripening of the barley crop; the age of the kids, lambs, and doves; the ripeness of the fruit trees; and the relation of the date to the tekufah (seasons). Through the Amoraic period (200–500 CE) and into the Geonic period, this system was displaced by mathematical rules. The principles and rules appear to have been settled by the time Maimonides compiled the Mishneh Torah in the 12th century.

Because of the roughly eleven-day difference between twelve lunar months and one solar year, the length of the Hebrew calendar year varies in the repeating 19-year Metonic cycle of 235 lunar months, with the intercalary month added according to defined rules every two or three years, for a total of 7 times per 19 years. The Hebrew calendar year is longer by about 6 minutes and 25+25/₅₇ seconds than the current mean solar year, so that every 224 years, the Hebrew calendar will fall a day behind the current mean solar year; and about every 231 years it will fall a day behind the Gregorian calendar year.

The era used at present is the Anno Mundi epoch (Latin for "in the year of the world"; Hebrew: לבריאת העולם, "from the creation of the world"). As with Anno Domini, the words or abbreviation (A.M. or AM) for the era should properly precede the date rather than follow it, although this is no longer always followed. This system of dating is also known as the "Hebrew era". AM 5772 began at sunset on 28 September 2011 and ended on 16 September 2012. AM 5773 began at sunset on 16 September 2012 and will end on 4 September 2013.