If the AsTime attribute for a SkyFrame axis is zero, then coordinates on that axis will be formatted as angles by default (using degrees, minutes and seconds), otherwise they will be formatted as times (using hours, minutes and seconds).
The default value of AsTime is chosen according to the sky coordinate system being represented, as determined by the SkyFrame's System attribute. This ensures, for example, that right ascension values will be formatted as times by default, following normal conventions.
AST A Library for Handling World Coordinate Systems in Astronomy