Answer
SYSDATE returns the current date and time according to the operating system clock on the database server itself. CURRENT_DATE returns the current date in the session's own time zone, which can differ from the server's if the session's time zone is set differently. DBTIMEZONE is the database's internal time zone setting, specifically used to interpret TIMESTAMP WITH LOCAL TIME ZONE column values correctly. To see the current time expressed specifically in the database's own DBTIMEZONE, use SELECT SYSTIMESTAMP AT TIME ZONE DBTIMEZONE FROM DUAL. Understanding this distinction matters whenever date/time values look inconsistent between different queries or reports — SYSDATE, CURRENT_DATE, and a value converted to DBTIMEZONE can each legitimately show a different time depending on server clock, session time zone, and database time zone settings respectively.