In V$LOGMNR_CONTENTS dictionary view the TIMESTAMP and COMMIT_TIMESTAMP columns are of DATE data type - without any timezone information. So which timezone are they in - database timezone, host timezone, or UTC? Is there a database parameter to configure their timezone?
I guess it is the time zone of database server's operating system. Simply because SYSDATE which might be used for insert is also returned in the time zone of database server's operating system.
Perhaps Oracle uses DATE data type instead of TIMESTAMP data type for historical reasons. I don't know when TIMESTAMP was introduced but certainly DATE came earlier.