calendar, Jewish

Religious and civil dating system based on both lunar and solar cycles. In the calendar used today, a day is counted from sunset to sunset, a week comprises 7 days, a month has 29 or 30 days, and a year has 12 lunar months plus approximately 11 days (or 353, 354, or 355 days). In order to bring the calendar in line with the annual solar cycle, a 13th month of 30 days is added in the 3rd, 6th, 8th, 11th, 14th, 17th, and 19th years of a 19-year cycle. Therefore, a leap year may have from 383 to 385 days. The Jewish calendar in use today was popularly accepted around the 4th century AD and is based on Biblical calculations placing the creation in 3761 BC.