## Changes Introduced in V3.7

The following describes the most significant changes which occurred in the AST library between versions V3.6 and V3.7:

1. Support for time coordinate systems has been introduced throught the addition of two new classes, TimeFrameTimeFrame and TimeMapTimeMap. The TimeFrame is a 1-dimensional FrameFrame which can be used to describe moments in time (either absolute or relative) in various systems (MJD, Julian EpochEpoch, etc.) and referred to various time scales (TAI, UTC, UT1, GMST, etc). The TimeMap is a MappingMapping which can transform time values between these various systems and time scales. Note, FitsChans which have a foreign encoding (i.e. any encoding other than NATIVE) are not able to read or write these new classes.