Skip to main content
Hong Kong Observatory Brand Hong Kong - Asia's world city
GovHK Traditional Chinese Simplified Chinese Search Search Site Map Contact Us
red dot
Print Version
Print Version PDF Version

Julian Date (JD) and Modified Julian Date (MJD)

Julian Day Number is a count of
days elapsed since Greenwich mean
noon on 1 January 4713 B.C.  The
Julian Date is the Julian day number
followed by the fraction of the day
elapsed since the preceding noon.
  Modified Julian Date (MJD) is
defined as:


Press below to see
the MJD today:


Last revision date: <20 Dec 2012>