IFD0 and XMP-XMP ModifyDate tags

[camner]

What kinds of changes/modifications to an image file should make the values of the IFD0:ModifyDate and XMP-XMP:ModifyDate tags change value? 

[Phil Harvey]

According to the specifications, this is supposed to be updated whenever the file is written.

- Phil

[camner]

Thanks.  I don't think either Lightroom or Adobe Bridge respect this.  I have made several changes to metadata with either or both of these and these tags are NOT rewritten.

[StarGeek]

They are probably only updating the MetadataDate when the change is only the metadata.

The EXIF standard says under the DateTime entry (which is the actual name of the ModifyDate)

In this standard it is the date and time the file was changed.

But later on, under Annex H.4 Category and Rank Relationship, which covers when a tag should be updated, it says


Which sounds more like editing of the actual image, at least to me.