Hello, I have tried this: exiftool "-DateTimeOriginal<ModifyDate"
However the Original is set to the current time in the system, despite the fact, that file has a ModifyDate. :-(
I think you are confused about what you are doing.
Whenever you write anything to the file, the FileModifyDate (the filesystem modification date/time) is set to the current time unless the -P option is used.
Also, read FAQ 3 (https://exiftool.org/faq.html#Q3) to learn how to better understand what is going on.
- Phil