Pyongyang doesn't observe daylight saving time but Hertford does. DST in Hertford started on 31 March 2019 and will end on 27 October 2019. Once DST ends in Hertford the time difference between Hertford and Pyongyang will be 9:0 hours.
Time zone: BST - British Summer Time (UTC/GMT +1)DST started on 31 March 2019DST will end on 27 October 2019Time zone difference / Flight distance
Time zone: KST - Korea Standard Time (UTC/GMT +9)Time zone difference / Flight distance