Historical dates

Explore core Jewish historical dates, Tohu and Mabul year-counting conventions, the Nissan and Tishri opinions, and accounts of extended days.

Compare the conventional Hebrew year with a selected historical count. Include or exclude the preliminary Tohu year and the Mabul year without changing the fixed calendar or astronomical calculations.

The creation tradition and the calculated calendar are shown separately: Friday for Adam HaRishon is mapped to 29 Elul 1, before the fixed calendar’s 1 Tishri 2. Compare Rebbi Eliezer and Rebbi Yehoshua in Rosh Hashanah 10b–11b.

Optional source cards describe Yehoshua’s extended day and Chizkiyahu’s shadow sign. These accounts are not converted into an assumed correction to calendar dates.

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.

JavaScript is required for the interactive explorers and calculations. The descriptions and navigation remain available without JavaScript.