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
Related systems & concepts
Knowledge connections
- Associated withTerrestrial Time
- Associated withCoordinated Universal Time (UTC)
- Associated withThe J2000 Epoch
Sources
The primary and reference sources this topic draws on.
- IAUInternational Astronomical Union
Official naming, definitions, constellation boundaries, and astronomical nomenclature.