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XMM-Newton Science Analysis System


selectlib (selectlib-4.69) [xmmsas_20070708_1801-7.1.0]

Meta Index / Home Page / Description / Arithmetic constants and identifiers

Times

Times can be expressed in either of the following ways:

form	comment	example
xxxx-xx-xxTxx:xx:xx[.xxx]	combined date-time string	2002-06-03T18:59:01.1
jdxxxxxx.xxx	Julian date	jd2450850.5
mjdxxxxx.xxx	Modified Julian Day	mjd50850.5
yxxxx.xxx	decimal year number	y2002.5
xxx xxx x xx:xx:xx xxxx	calendar date	Mon Jun 3 18:21:19 2002

x stands for a single decimal digit, jd, mjd, y, T are literal character strings and square brackets denote optional items. The number of shown digits after the decimal point is not significant. In an arithmetic context all given times evaluate to the number of elapsed seconds since the fixed time 1998-01-01T00:00:00 TT.