Selection of a particular coordinate system is performed simply by setting a value for the TimeFrame's (character string) System attribute. This setting is most conveniently done when the TimeFrame is created. For example, a TimeFrame representing Julian Epoch would be created by:
Note that specifying “SystemJEPOCH” also changes the associated
default Unit (from days to years). This is because the default value
of the TimeFrame's Unit attribute depends on the System attribute setting.
You may change the System value at any time, although this is not usually needed. The values supported are set out in the attribute's description in Appendix C.