Currently, I'm trying to change the value - for 79 JPEGs - of the Date Subject Created ({File.MD.XMP::photoshop\DateCreated\DateCreated\0}).
All is well, except for when I actually go to commit the change, with a metadata write-back. This causes the newly-assigned value to revert back to the prior value.
Reasons? Changes I can/should make?
Check the file with the Metadata Analyst. This is a typical "out-of-sync" issue.
See Metadata Problems and Pitfalls (https://www.photools.com/help/imatch/#md_for_beginners.htm?dl=md_problems) in the IMatch help for typical problems with metadata and how to fix them.
I have already tested some of these files with Metadata Analyst. And, they all check out fine! So, it has to be something else.
Then provide a sample file which exhibits the problem so we can look at it. We don't know which file format you use, if ExifTool issues any warnings (Output Panel) after write back etc.
In my experience, when the date does not stick, it is overridden by some other tag in the file, most often legacy IPTC metadata.
Or maybe ExifTool cannot write to the file (check Output panel) because the user has insufficient file system permissions (had that last week in email support) or the file is corrupted and ExifTool thus cannot write to it (had that also last week).
At your request, I'm making available here, a sample image (in the ZIP file attachment).
I have downloaded the image and added it to my test database.
I then changed title, description, headline, create date and date subject created (current date and time, current date and noon).
I wrote back.
No errors or warnings. All modified metadata is written correctly. Timestamps show the updated date and time, both in IMatch and in the metadata in the file.
I see no issues or problems.
Well, if that's the case on your end, could it be that I have a setting - in Preferences->Metadata OR Metadata 2 - that is prohibiting the change at write-back, because the Date Subject Created Timestamp is write-protected?
Specifically, I did not change the title/description/headline/create date.
I simply used MD Mechanic to set the Date Subject Created to the current value of the Microsoft Date Acquired. This operation is seemingly successful. That is, until I write-back. Then, Date Subject Created reverts back.
If I change the date and time only in the Metadata Panel, I get the same positive result. The new dates and times are safely written to the file and persist.
You did not mention that you manually set the date and time via the Metadata Mechanic.
Information like this would be very helpful, because it prevents wasting time.
When you directly manipulate metadata that way, pay extra attention that whatever variable you use produces the required date and time format required. This is explicitly mentioned in the help, e.g: Use the Correct Format (https://www.photools.com/help/imatch/#md_templates.htm?dl=h-18)
Variables by default return dates and times in your local format which is not suitable for directly setting metadata values. You are responsible to format them correctly if you directly manipulate metadata.
I'm sorry. Now, I know, that MD Mechanic requires a user-setting, as formatting the text, whereas the MD Panel already self-applies this already.