Astronomy and astrophysics Spherical astronomy and astrometry Concept
Julian day
Summary
The Julian day is a continuous count of days used by astronomers, starting at noon on 1 January 4713 BC in the proleptic Julian calendar. The Julian date adds the fraction of the day since the last noon, so one real number gives an instant of time. Differences of Julian dates give time intervals directly, with no months, leap years or calendar reforms in the way.
Further reading
About this page
| Tag | DWS7SD01BS |
|---|---|
| URI | m2://DWS7SD01BS |
| Kind | concept |
| Writing | W0 stub |
| MSC | 85A04 |
| Same as | |
| Changed | 3 November 2026 |
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