You cannot change file time stamps from within Mp3tag as you will.
You can try to reach your goal using "Total Commander" with "Anytag" plugin.
1. Necessary requirements.
Total Commander with content plugin "anytag.wdx" installed.
2. If not already done, then edit the text file "anytag.any".
... or ...
... append a user defined tag field of datatype string (8) into "anytag.any",
e. g. "8|Extra_DateTime|%Extra_DateTime%"
... and use this new tag field further on in the process.
If changes were made to the "anytag.any" file, then Total Commander must be restarted to reflect the changes.
3. Prepare the media files using Mp3tag.
Use the existing tag field "YEAR"
... or ...
... create a user defined tag field "EXTRA_DATETIME" in each file.
The Mp3tag tag field "YEAR" (... respectively "EXTRA_DATETIME") must have a format, which Total Commander can accept as proper data to set file time attributes.
Fill the tag field with the necessary data.
The format of the DateTime data string can be one of the following formats:
The format of the DateTime string might depend on your local computer DateTime settings.
Above DateTime format examples work on a computer set accordingly to ISO 8601.
4. Use Total Commander with Anytag plugin.
Select the file to work on.
Open menu option to change file atributes.
In the upcoming dialog choose "Plugin/More Attributes"
A new line with edit fields comes up.
Plugin "tc" "comment" is already filled in.
Press the "+" button, choose a field name "anytag>Year" (... or ... "anytag>Extra_DateTime").
Change plugin tc property to "Create Date" or "Modification Date" as you need it.
(Note: This "More Attributes" dialog's behaviour is somewhat strange and might carry a bug or more, because the fields from the anytag plugin are sometimes not displayed in the field list.
But doing the steps as described before will work.)
If the changes to the dialog are made, then press "OK".
Total Commander will make the changes to the selected files.
There will come up a warning message in case of DateTime format is not correct.
Then press "Abort" and make sure (... use Mp3tag) that all DateTime strings in the tag fields "YEAR" (... respectively "EXTRA_DATETIME") have an acceptable correct format.
Repeat step 4.
5. Check result.
To check what changes are made to the file, select the file in Total Commander, press "Alt+Enter".
A properties dialog window comes up, which displays the three file related DateTime values: Create DateTime, Modified DateTime, Last Access DateTime.