This chapter aims at collecting brief definitions of the various time systems in use, as well as simple formulae for doing transformations. The last section describes the time as it is kept in the RXTE FITS tables.
Information is available on absolute time calibration .
Time and Date Systems See also the USNO Time Scales page. Based on the SI second and derived from a large number of clocks all over the world. Reduced to mean sea level. Based on the SI second, it knows days of 86400 and 86401 seconds. The latter are days with a so-called leap second.