The Hebrew calendar (Hebrew: הלוח העברי)
or Jewish calendar is the annual calendar used in Judaism. It determines
the dates of the Jewish holidays, the appropriate Torah portions
for public reading, Yahrzeits (the date to commemorate the death
of a relative), and the specific daily Psalms which some customarily
read. Two major forms of the calendar have been used: an observational
form used prior to the destruction of the Second Temple in 70 CE,
and based on witnesses observing the phase of the moon, and a rule-based
form first fully described by Maimonides in 1178 CE, which was adopted
over a transition period between 70 and 1178.
Hebrew calendar (הלוח העברי
ha'luach ha'ivri), or Jewish calendar, 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 reading, among many ceremonial uses. In Israel, it
is an official calendar for civil purposes and provides a time frame
Originally the Hebrew calendar was used by Jews for all daily purposes,
but following the conquest of Jerusalem by Pompey in 63 BCE (see also
Iudaea province), Jews began additionally following the imperial civil
calendar, which was decreed in 45 BCE, for civic matters such as the
payment of taxes and dealings with government officials.
The Hebrew calendar has evolved over time. For example, until the
Tannaitic period, the months were set by observation of a new crescent
moon, with an additional month added every two or three years to keep
Passover in the spring, again based on observation of natural events,
namely the ripening of barley to reach the stage of "aviv"
(nearly ripened crop). Through the Amoraic period 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 a repeating 19-year Metonic cycle of 235 lunar months, with
an intercalary lunar month added according to defined rules every
two or three years, for a total of 7 times per 19 years. Seasonal
references in the Hebrew calendar reflect its development in the region
east of the Mediterranean and the times and climate of the Northern
Hemisphere. The Hebrew calendar year is longer by about 6 minutes
and 25+25/57 seconds than the present-day mean solar year, so that
every 224 years, the Hebrew calendar will fall a full day behind the
modern solar year, and about every 231 years it will fall a full day
behind the Gregorian calendar year.
The present counting method for years use the Anno Mundi epoch (Latin
for "in the year of the world", לבריאת
העולם), abbreviated AM or A.M. and also
referred to as the Hebrew era. Hebrew year 5770 began on 19 September
2009 and ended on 8 September 2010. Hebrew year 5771 (a leap year)
began on 9 September 2010 and ends on 28 September 2011.