Explore Jewish time through astronomy.
Shaot Zmaniyot: Proportional Hours
How a selected day interval is divided into twelve proportional hours for zmanim calculations.
The term
Shaot zmaniyot are proportional or seasonal hours. Divide the duration of a defined daytime interval by twelve to obtain one such hour. Its length changes with the selected boundaries, date and location.
Calculation and interpretation
If a defined interval lasts 13 civil hours, each proportional hour lasts 65 minutes. The arithmetic is straightforward; the choice of day boundaries is the interpretive part. Sunrise-to-sunset and other definitions need not give the same results.
Use in Jewish Cosmology
Settings specify the definitions used by the zmanim calculations. The Halachic Times explorer presents the corresponding events and solar context. At locations or seasons without the required boundary events, a missing result should not be replaced by an unstated alternative rule.
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About Jewish Cosmology
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.
Models, terminology and limitationsHalachic times are unverified, have no rabbinic approval, and must not be relied upon for practical halachic decisions unless and until an appropriate authority approves them.