A Julian epoch is an epoch that is based on Julian years of exactly 365.25 days.

Julian epochs are used in preference to the old Besselian epochs.

Julian epochs are calculated according to:

J = 2000.0 + (Julian date - 2451545.0)/365.25

The standard epoch currently in use is J2000.0, which corresponds to January 1, 2000 12:00 Terrestrial Time.