UTC, barycentric time, MJDs, etc. – What does Kepler use?
There are several FITS keywords in the Kepler data headers that relate to time, and these have been updated for the June, 2010 release. As of this release only calendric dates are given in the primary headers of the FITS light curve files. The FITS extensions give MJD (Modified Julian Dates) referred to UTC and are barycentric corrected, as noted in the keyword descriptions. Technically, the time system is referred to as Barycentric Dynamical Time (TDB), except that unlike the formal definition of TDB no periodic relativistic correction (which amounts to no more than 1.6 milliseconds), has been applied. Changes to these conventions occur (so far) often, so please refer the appropriate Data Release Notes version. The version number is given as the DATA_REL keyword in the extension header. • What is the reference time for Kepler data? For Kepler, the reference time is the end time. In the Kepler Instrument Handbook, Section 7.3, users are warned against assuming a precision of better tha
