Mp3tag / "Date Modified" file attribute

I haven't paid a lot of attention to this detail, but I just retagged a FLAC file by adding additional Vorbis comments. It seems strange to me that after doing that, neither the file size nor the Date Modified changed. How can this be? I'm using version 2.69 on a 64-bit Window 7 Pro workstation.

Dennis....aka "d2b"

Check Mp3tag options "Tag ... Timestamp".
To prevent rewriting of big sized FLAC files, such files having the VORBIS COMMENT tag can provide some empty room within the tag for smaller updates of the tag.