Wrong age of person at DNG

[Rene Toepfer]

I have a DNG file and marked a person. The person's DOB ist 2015-02-27 and the DNG created on 2021-02-20, see attachement 2021-03-14_10-13-03.png.
Several changes occured on 2021-02-21. Now IMatch shows that the age of this person is 6 instead of 5.
As far as I understand the calculation of the age, IMatch uses either EXIF:Creation Date/Time or (if not available) creation date/time of file system.

[Mario]

IMatch uses the DOB you enter for the person and the date subject created as set in the Metadata panel.
File system timestamps are only used as a last resort fallback if a file has no usable metadata. See How IMatch uses Date and Time Information

Always ensure that you have proper XMP date created / date subject created set and write back once to persist the info.
Else IMatch will have to fall back over and over again to the last modified file system timestamp.

You may want to enable the option Edit > Preferences > Metadata 2: Mark file as pending write-back so you see when IMatch had to set these time stamps from a secondary source (e.g. file system timestamp).

[Rene Toepfer]

The DOB is given correct, with ARW files it works well and the XMP:Creation Time will not be changed.
At the DNG the XMP:Creation Time is set to today. How can this be? If I set the date back as per EXIF the age is correct. The same applies for all other DNG afterwards I did a write-back. For DNG I use sidecar XMP files instead of modifying the native DNG.

[Mario]

I did not mention creation time anywhere.
Did you read the help topic?
Did you look at "date created" and "date subject created" in the Metadata Panel?

The relevant timestamp is subject created or date created if the first one does not hold data.
IMatch derives the global File.DateTime value from that info, which is also used for the timeline, the File Window and other features.
Make sure date subject created and date created are correct and set in the file (and don't change every time you modify the file).

[Rene Toepfer]

I solved this issue. It is NOT related to IMatch but to my preprocess, I have since several years.
If I copy my files from sd card/mobile to my drive I run the exiftool to rename the files based on creation date/time and add some tags. I have not set the -P argument of the exiftool which keeps the creation date/time unchanged. Meanwhile I have added this argument to my script and everything works as expected.

[Rene Toepfer]

Did you look at "date created" and "date subject created" in the Metadata Panel?

Yes, that was one of my main tags.

Make sure date subject created and date created are correct and set in the file (and don't change every time you modify the file).

Yeap, that was the reason, I have not considered this.