Calendar Structure Months in the Jewish Calendar Month NamesĪ year in the Hebrew calendar can be 353, 354, 355, 383, 384, or 385 days long. In comparison with the timing of the astronomical seasons, it is off by 1 day every 216 years. The Hebrew calendar is a comparatively imprecise system in terms of reflecting the duration of a solar year, which is the time it takes Earth to complete a full orbit around the Sun. Featuring a body of complex regulations, exceptions, and mathematical rules, it is also designed to satisfy a number of requirements conveyed in the Jewish Holy Scripture. Jewish time reckoning is lunisolar, which means that the calendar keeps in sync with the natural cycles of both the Sun and the Moon.