Cycles

Explore the 19-year machzor, leap years, the 28-year solar cycle, planetary hours and the zodiac year with precession.

Choose a Hebrew year, then expand a cycle card. Use Previous cycle and Next cycle to browse the 19-year and 28-year tables. Hebrew dates appear first, with local civil dates and times beneath them.

19-year machzor: each row shows the cycle number, the year’s position, its length and keviah, Cheshvan and Kislev lengths, and the weekdays of Pesach, 9 Av and Rosh Hashanah. The three keviah letters describe the weekday of Rosh Hashanah, whether the year is deficient, regular or complete, and the weekday of Pesach.

28-year solar cycle: cycles begin with years 1, 29, 57 and so on. The table follows Shmuel’s Tekufas Nisan through all 28 years. Traditional hours are counted from 18:00 on the Jerusalem standard clock. The Koheles column assigns the 28 times in Koheles 3:2–8 in their textual order to years 1–28.

Planetary cycle: follow the repeating order of the seven planetary hours, the first ruler of each Hebrew night and day, and the seven four-year periods within the solar cycle, as described in chapter 6 of Pirkei deRabbi Eliezer.

Leap-year cycle: the highlighted positions are 3, 6, 8, 11, 14, 17 and 19, remembered as גו״ח אדז״ט. These seven years have 13 months; the other twelve years have 12 months, giving 235 months in a complete machzor.

Zodiac cycle: the current mazal at each entry appears first, beside its original classical assignment at year 1 or J2000. The classical sectors remain 30° each, with Sartan at 90°–120°. Colours follow each named mazal. Dates show entry and end; the planetary column shows the ruling hour and first night/day rulers at entry. Names follow Settings.

Jewish Cosmology is an interactive research and educational web application connecting Hebrew dates, traditional Jewish calendar calculations and halachic concepts of time with the observable motions of the Sun, Moon and planets, astronomical seasons and eclipses.

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