Modified Julian Day Timescale

Range

The Modified Julian Day (MJD) timescale is a continuous timescale starting in the remote past and continuing through today on into the remote future.  

Purpose

Functions that accept MJD time values provide information about the sun that (has and will) vary from instant to instant over the course of the history of the earth.

Function

MJD times may be calculated using the sdMJDx function.

Example

The MJD of 2000 Jan 1, at 00:00 UT equals 51544.0

Definition

The MJD used in this program is based on UT.

The MJD timescale is derived from the Julian Day (JD) timescale. The JD is a day count from Jan 1, 12:00 noon 4712 B.C.

The MJD is defined as JD - 2,400,000.5

The Gregorian calendar reform is incorporated into the MJD used by this program.  The day after October 4th, 1582 is October 15th.  In this program October 5th-14th, 1582 have not been assigned MJDs.

The earliest time supported by MJD in this program is Jan 1, 12:00 noon UT 4711 B.C., the latest is the end of the year 9999 A.D.

For further information about the MJD timescale see: Modified Julian Day