realme UI 7.0 & 6.0: Settings > System & update> Date & time > Dual clock > Clock 2
realme UI 5.0 & 4.0 & 3.0: Settings > System/Additional settings > Date & time > Dual clock > Usual residence
realme UI 2.0: Settings > Additional settings > Date & time > Dual clock > Usual residence
realme UI R & Go & T & S & U Edition: not support dual clock