I tried to use pvget to get just the secs and nanosecs (but not userTag) of a timestamp:
pvget -m -r "field(dataTimeStamp.secondsPastEpoch,dataTimeStamp.nanoSeconds)" adImage
but got an error message:
terminate called after throwing an instance of 'std::invalid_argument'
what(): duplicate fieldName dataTimeStamp
Issue is with CreateRequest utility with two subfields of a structure subfield, (although exception comes from FieldCreate implementation).