The Jewish lunar calendar: why the year is 5787
The year 5787 and the traditional epoch
In October 2026 the Jewish calendar is in the year 5787. On 25 October 2026 the corresponding civil and Hebrew dates are Sunday, 14 Cheshvan 5787, until sunset. The traditional year count is reckoned from an epoch associated with creation, rather than from the founding of the State of Israel or the destruction of the Second Temple. That epoch is conventionally placed in 3761 BCE by the familiar civil-calendar comparison. It is a religious and chronological convention, not a scientifically established date for the origin of the world.
A calendar of moon and sun
The Hebrew calendar is lunisolar. Months roughly follow the moon, beginning near the new moon, while leap months prevent festivals from drifting through the seasons. Seven years in a 19-year cycle add an extra month of Adar. This matters because Passover must remain a spring festival even though twelve lunar months are shorter than a solar year. A normal Hebrew year therefore lasts about 354 days, with variations, while a leap year is longer.
When the system took its familiar shape
In biblical and Second Temple times communities relied on observation and calendrical decisions. Over centuries calculations became more standardized. Later tradition connects the fixed calendar with Hillel II in the fourth century CE, although the detailed historical process is more complicated than a single reform on a single day. Calendar arithmetic includes postponement rules, the lengths of Cheshvan and Kislev, and leap-year scheduling. The modern civil calendar and Jewish calendar should not be treated as interchangeable.
From sunset to sunset
Jewish days begin at sundown, which is why Shabbat and religious holidays begin the previous civil evening. Rosh Hashanah begins the Hebrew year, but the religious month numbering starts with Nisan. The difference can initially confuse visitors to Israel. In everyday life, the Gregorian date is common in administration, while the Hebrew calendar continues to organize holidays, memorial dates, yahrzeits, weddings and communal observance.
Sources and further reading
Updated: October 2026