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," the North's official KCNA news agency said.
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."
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Seoul's Unification Ministry, which deals with cross-border affairs, said it was aware of the announcement but had no immediate reaction.
South Korea had similarly changed its standard time in 1954 -- again to reflect the break from Japanese rule -- but reverted to Japan standard time in 1961 after Park Chung-Hee came to power in a military coup.