I recently added a video from my phone into Immich, but it did not have the (approximate) correct date and time. Because I am leveraging Immich’s external library functionality and the Docker container’s mount point is read-only, Immich is unable to create the XMP sidecar.
The following exiftool command creates an XMP sidecar file with the desired CreateDate property. The resulting file gets copied to the directory that is designated as the external library. Finally I ran the discover job such that Immich picks up the XMP sidecar.
$ exiftool -tagsfromfile 20241231224307.m4v -xmp:CreateDate="2024:12:31 22:43.07.00-08:00" 20241231224307.m4v.xmp