North Korea announced on Friday that it was moving its clocks back by 30 minutes to create a new "Pyongyang Time" -- breaking from a standard imposed by "wicked" Japanese imperialists more than a century ago.
The change will put the standard time in North Korea at GMT+8:30, 30 minutes behind South Korea which, like Japan, is at GMT+9:00.
North Korea said the time change, approved on Wednesday by its rubber-stamp parliament, would come into effect from August 15, which this year marks the 70th anniversary of the Korean peninsula's liberation from Japan's 1910-45 colonial rule.
"The wicked Japanese imperialists committed such unpardonable crimes as depriving Korea of even its standard time while mercilessly trampling down its land," North Korea's official KCNA news agency said.
Standard time in pre-colonial Korea had run at GMT+8:30 but was changed to Japan standard time in 1912.
KCNA said the parliamentary decree reflected "the unshakeable faith and will of the service personnel and people on the 70th anniversary of Korea's liberation."
Seoul's Unification ministry, which deals with cross-border affairs, said a different time zone between north and south posed a number of possible challenges, including for operations at the jointly-run Kaesong industrial complex that lies just inside North Korea.
"In the short term, there might be some inconvenience in entering and leaving Kaesong," ministry spokesperson Jeong Joon-Hee told reporters.
"And in the longer term, there may be some fallout for efforts to unify standards and reduce differences between the two sides," Jeong said.
South Korea had similarly changed its standard time in 1954 -- again to reflect the break from Japanese rule -- but reverted to Japanese standard time in 1961 after Park Chung-Hee came to power in a military coup.
Park's rationale was partly that the two major US allies in the region -- South Korea and Japan -- should operate on the same time to facilitate operational planning.
Analysts said Pyongyang's time shift was aimed at shoring up the official narrative that paints North Korea as the pure, "authentic" Korea and South Korea as a land polluted by foreign domination.
"The North has always sought to project this image of being more aggressive in wiping out traces of Japanese colonial rule," said Yang Moo-Jin at the University of North Korean Studies in Seoul.
"So this falls in line with its claim to be the only legitimate Korean regime on the peninsula, and its dismissal of the South as a 'puppet regime' still sticking to corrupt colonial practices," Yang said.