Other Time Scales
Julian day number is a count of days elapsed since Greenwich mean noon on 1 January 4713 B.C., Julian proleptic calendar. The Julian Date is the Julian day number followed by the fraction of the day elapsed since the preceding noon. Conveniently for astronomers, this avoids the date skip during an observation night.
Modified Julian day (MJD) is defined as MJD = JD - 2400000.5. An MJD day thus begins at midnight, civil date. Julian dates can be expressed in UT, TAI, TDT, etc. and so for precise applications the timescale should be specified, e.g. MJD 49135.3824 TAI.
Read more about this topic: Time Standard
Famous quotes containing the words time and/or scales:
“Literature exists at the same time in the modes of error and truth; it both betrays and obeys its own mode of being.”
—Paul Deman (1919–1983)
“In what camera do you taste
Poison, in what darkness set
Glittering scales and point
The tipping tongue?”
—Wallace Stevens (1879–1955)