Kim Jong Un LINKED TO FRIDAY ADVANCE PAGE already rules North Korea like a medieval despot, but his latest eccentricity is actually trying to turn back time. To mark the 70th anniversary of victory over the “wicked Japanese imperialists”, the poobah of Pyongyang has decreed that his country will set its clocks half an hour later to reject the timezone Japan imposed during its occupation of the Korean peninsula.

Eccentric it may be, but there is a history of rulers changing time zones to assert their power. When such decisions institutionalise real authority, they look masterful; when they substitute for it, they range from in-secure to absurd.

Time zones were forced by new technology but shaped by political whim. They emerged as the agricultural pulse set by the sun was replaced by the grinding rhythm of industry. In the agrarian mid-19th century the US had more than 300 time zones. As railways took over, a private sector solution emerged: in 1883 railroad companies imposed the four time zones that still exist.