TZ_OFFSET returns the time zone offset from Coordinated Universal Time (UTC).
VARCHAR2
TZ_OFFSET({ 'time_zone_name' | '{ + | - } hh:mi' | SESSIONTIMEZONE | DBTMEZONE } )
time_zone_name is the name of a time zone.
hh:mm are hours and minutes. This argument simply returns itself.
SESSIONTIMEZONE returns the session time zone.
DBTIMEZONE returns the database time zone.
TZ_OFFSET('US/Eastern') returns the offset -04:00 during Daylight Savings Time.
TZ_OFFSET('EST') returns the offset -05:00.
TZ_OFFSET(DBTIMEZONE) returns the offset -07:00 for Mountain Standard Time.