How to store ISO-8601 in XMP?

[Tom OReilly]

I would like to write an ISO-8601 timestring verbatim to XMP metadata, including decimal seconds, e.g. "2020-03-12T17:34:08.987Z"

My configuration file defines:

%Image::ExifTool::UserDefined = (
   # XMP tags may be added to existing namespaces:
   'Image::ExifTool::XMP::xmp' => {
 
      # Trigger time in ISO-8601 format
      CameraTriggerTime => { Groups => { 2 => 'Other' } },
      
   },
);
 
1;
 

When I write CameraTriggerTime, the 8601 format is somehow being altered by exiftool, e.g.:

$ exiftool -config test.config  -xmp-xmp:CameraTriggerTime=2020-03-12T17:34:08.987Z test.jpg
    1 image files updated
$ exiftool -S test.jpg | grep Trigger
CameraTriggerTime: 2020:03:12 17:34:08.987Z

Why is the string format being changed? How can I write "2020-03-12T17:34:08.987Z" verbatim as an XMP tag?
Or is there an exiftool feature that will store an ISO-8601 time like this?

Thanks!

[Phil Harvey]

Hi Tom,

It is being written verbatim, but changed to standard ExifTool format when reading.  To avoid it being changed when reading, either use your config file or set the API XMPAutoConv option to 0 with -api xmpautoconv=0.

- Phil