Time scale · JD

Julian Date

A continuous count of days (and fractions) since noon Universal Time on 1 January 4713 BC in the proleptic Julian calendar, used throughout astronomy to timestamp observations without the awkwardness of calendar months and leap years. The Modified Julian Date (MJD = JD − 2400000.5) shifts the origin to a recent midnight for convenience.

Highlights

›A single running day-count for timestamping observations

Terrestrial Time
Coordinated Universal Time (UTC)
The J2000 Epoch

Knowledge connections

Associated withTerrestrial Time
Associated withCoordinated Universal Time (UTC)
Associated withThe J2000 Epoch

Sources

Facts on this topic will be cited from these primary and reference sources.

IAUInternational Astronomical Union
Official naming, definitions, constellation boundaries, and astronomical nomenclature.

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Julian Date

Highlights

Related systems & concepts

Knowledge connections

Sources

Julian Date

Highlights

Related systems & concepts

Knowledge connections

Sources