These are the unversioned properties that Subversion reserves for its own use:
If present, contains the authenticated username of the person who created the revision. (If not present, the revision was committed anonymously.)
Contains the UTC time the revision was created, in ISO 8601 format. The value comes from the server machine’s clock, not the client’s.
Contains the log message describing the revision.
If present, the revision was created via the autoversioning feature. See Autoversioning.