The Democratic People's Republic of Korea (DPRK) on Friday at 23:30 local time (15:00 GMT) adjusted country's clocks 30 minutes forward to midnight as to be in the same time zone as the Republic of Korea's (ROK).
The DPRK's state media said the reset is the "the first practical step" to speed up Korean unification.
During the April 27 talks between DPRK leader Kim Jong Un's and ROK President Moon Jae-in, Kim told Moon it was "a painful wrench to see two clocks indicating Pyongyang and Seoul times hanging on a wall of the summit venue."
He then promised to change its country's time zone to that of the ROK.
Meanwhile, U.S. President Donald Trump on Friday said the date and location have been set for the summit between Kim and himself.
A brief history of the DPRK's time zone
The DPRK created "Pyongyang Time" in 2015 by setting its clocks 30 minutes behind the ROK and Japan.
It said at the time that it did so to root out the legacy of Japan's 1910-1945 colonial rule of the Korean Peninsula, when clocks in peninsula were changed to be the same as in Japan.
"The wicked Japanese imperialists committed such unpardonable crimes as depriving Korea of even its standard time while mercilessly trampling down its land," KCNA wrote.
The ROK's timezone moved away from Japanese time in the 1950s but switched back again in the 1960s.
Trump-Kim summit: Date, place set?
"We have a date, we have a location," Trump told reporters on Friday but still didn't reveal either the date or place of the summit, only claiming to have an announcement soon.
The White House has said first meeting ever between sitting US and the DPRK leaders could take place in the coming weeks.
This week, Trump expressed a preference for the DMZ but also said Singapore was possible.
However, Prime Minister Lee Hsien Loong said last week that Singapore's government had no formal invitations or requests from any of the parties.
The summit was suggested and provisionally agreed in March, after a ROK delegation met Kim in Pyongyang and later visited the White House.
The White House confirmed later on Friday that Trump will host Moon on May 22 to discuss upcoming Kim-Trump summit.
Trump also denied suggestions that he was considering taking US troops out of the ROK as part of the negotiations with the DPRK.
