North Korea has switched to a new time zone, turning its clocks back by 30 minutes to mark its liberation from the Japanese at the end of the second World War.
Bells rang out in the capital Pyongyang at midnight on Friday as the new time zone came into effect.
North Korea's announcement of the move to "Pyongyang time" surprised South Korea which warned the president ran counter to efforts to foster co-operation.
Korea had used 127 degrees 30 minutes east - the longitude that state news agency KCNA said would be used for the new time zone - when it first introduced the concept of an official time zone in 1908.
Japan ruled the Korean peninsula from 1910 to 1945. A decree by colonial Japan in 1912 moved the time line to where Korea Standard Time is currently set, 135 degrees east longitude.
So, until this morning, the North had been nine hours ahead of GMT - like South Korea and Japan.
North Korea's chief astronomer Jong Sok said changing time zones made a lot of sense - and was appropriate as the country marked 70 years since it was liberated from Japanese rule.
“With the time standard that we have used up until now, the time when the sun is at its highest position is not correctly noon,” he told the Associated Press.
“I think it is the lawful right of a sovereign state that our republic - to mark the 70th anniversary of our liberation and the 70th anniversary of the defeat of Japanese imperialism - has announced our time as Pyongyang Time, the same as our ancestors used and which was robbed from us by the Japanese imperialists.”
KCNA said earlier this week: “the wicked Japanese imperialists committed such unpardonable crimes as depriving Korea of even its standard time while mercilessly trampling down its land with 5,000 year-long history and culture and pursuing the unheard-of policy of obliterating the Korean nation”.
South Korean president Park Geun-hye said on Monday Pyongyang’s “unilateral” decision, taken without any consultation with Seoul, was “highly regrettable” and threatened a “further deepening of disparity between the two Koreas”.