Seoul: South Korean President Park Geun-Hye on Monday criticised the North`s "regrettable" decision to turn back its clocks to a new time zone, saying it would deepen divisions between the two rivals.
North Korea announced Friday that it was changing its standard time to GMT+8:30, 30 minutes behind South Korea.
Pyongyang offered a nationalist rationale for the move, saying it would return the North to an original time zone used before Japan imposed Tokyo standard time during its 1910-45 colonial rule of the Korean peninsula.
The new system is to take effect on August 15 this year -- the 70th anniversary of the peninsula`s liberation from Japanese rule.
"It is highly regrettable that the North unilaterally changed its time zone with no consultation with us," Park said during a meeting with senior aides.
Noting that Pyongyang`s move had triggered international criticism, Park said it also threatened a "further deepening of disparity between the two Koreas."
Inter-Korean ties have been icy for years following a series of nuclear and long-range missile tests by the North and occasional military clashes along the border.
Pyongyang in recent months rejected a series of dialogue offers, citing Seoul`s refusal to halt annual military exercises with the United States.
"The North`s action to break from the shared standard time ... runs counter to efforts to foster inter-Korea cooperation and to achieve reunification," Park said.
The two neighbours -- whose division was sealed by the 1950-53 Korean War -- technically remain at war after the conflict ended with a ceasefire instead of a peace treaty.
Park has often described unification as a top priority, but critics say many of her policy goals lack concrete steps and point to the absence of any high-level official talks since February 2014.
Cross-border tensions are expected to escalate since Seoul on Monday vowed to retaliate after blaming North Korea for planting landmines that maimed two soldiers on border patrol.