Related to this:
[ul][li]If you want to set the Date Modified timestamps on the files, based on the dates in the filenames, see: File name to Modified Date/Time.[/li]
[li]If you want to set the Date Modified timestamps from EXIF shooting times, or vice versa, see: Copy Created/Modified times to/from EXIF times.[/li][/ul]
Depending on what you are doing, those may be preferable since they allow you to sort by the normal date fields, which will work both in and outside of Opus, without modifying the file descriptions.