North Korea has shifted its clocks backward by 30 minutes this morning. The occasion was marked by bells which rang out in the capital Pyongyang at midnight on Friday as the new time zone came into effect. The new time zone was announced by leader Kim Jong-un last week.
Its state news agency KCNA said Korea's standard time had been changed during occupation by "wicked Japanese imperialists".
North Korea is currently nine hours ahead of GMT and in the same time zone as neighbouring South Korea and Japan.
The move has led to concerns that efforts to reduce tensions between North and South Korea could be hampered.
It could affect work at North Korea's Kaesong industrial plant which is run by both countries.
As reported by the BBC, Unification Ministry official Jeong Joon-Hee said: "And in the longer term, there may be some fallout for efforts to unify standards and reduce differences between the two sides."
There is no international body that approves a country’s change of time zone, as countries decide for themselves.
In 2011, Samoa changed its time zone to the other side of the international dateline, losing one day, so as to make communication easier with neighbours Australia and New Zealand.