Types of Julian Date
More information about Julian Date is on the Time Scales page under the heading "Based on Earth's Rotation: Mean Solar Time"
Conversions are found here.
Conversions are found here.
Reduced JD
MJD: Modified Julian Date
Mars Sol Date
MJD: Modified Julian Date
- Created to keep with civil usage and the International Meridian Conference of 1884
- days reckoned from midnight, number of days elapsed since 1858 November 17.0
- made numbers much smaller
- defined in 1950s as JD – 2400000.5
- introduced by NASA/Goddard for spacecraft applications
- 4 digit day count from MJD 40000 represented by 14-bit binary number
- recycled to 0 on MJD 50000 (October 10, 1995) since code limited to 4 digits
- number of days elapsed since epoch of solar and lunar ephemerides used from 1900 through 1983
- defined by IAU at meeting in Dublin, Ireland
- count of days of the Gregorian calendar
- integer applied to whole day, day 1 was October 15, 1582 (day that Gregorian calendar went in to effect)
- named for Aloysius Lilius, principle author of Gregorian calendar
- invented by Brice G. Ohms of IBM, 1986
- part of date conversion routines part of IBM language Environment (LE software)
- system used in REXX, Go and Microsoft .NET
Mars Sol Date
- solar date on Mars
- same as Julian day except adjusted to frame of reference of Sun, can differ from Julian day by as much as 8.3 minutes (time it takes for Sun’s light to reach Earth)