How to add a date to iPhone movie files

[dlgkjfgkwrj]

It seems that iPhone movie files (.MOV) have a Keys:CreationDate tag in the format 2020:05:02 16:09:44-04:00

The application I am using doesn't understand how to use that key and instead uses System:FileModifyDate (and ignores the timezone)

Is there anywhere I can copy the date, like EXIF, XMP, where there might be a better chance of the date the video was taken being recognized with its time zone?

[StarGeek]

Possibly, but it's also quite possible, even probably, that the app doesn't read anything else.  Quite a few programs will ignore the embedded time stamps in video files.  To add to that, because two of the most important time stamps are supposed to be in UTC, there are plenty that will read it incorrectly.

Additionally, though you can add XMP data to a video, almost no program other than Adobe programs will read it.  EXIF and IPTC data can't be added to a video.

It might help if you give the name of the app.

I would suggest this command.  It will update the most common time stamps as well as the file system ones.
exiftool -api QuickTimeUTC "-AllDates<CreationDate" "-FileModifyDate<CreationDate" "-FileCreateDate<CreationDate" /path/to/files/