PDS3 file source. This is pointed at PDS3 LBL ("label") files and will return data they describe.
here is the one place for this logic which identifies if the column contains timetags.
look through the PDS label document to see if dependencies can be identified. Presently, this is simply one other dataset with the same axis (as in sample_offset) or the same axis name as something that has a time unit (Epoch).