The date was pinpointed using testimonies from Kenji Fujimoto, a Japanese chef who worked for the Kim family, North Korean defectors and Kim's childhood friends at the Liebefeld school in Bern, Switzerland, where he briefly studied as a teenager.

However there were few signs of celebration yesterday in Pyongyang.

North Korea used to treat the birthdays of Kim's father and grandfather as national holidays, throwing extravagant festivals and handing out presents to the public.

Some experts wondered if the relatively muted celebration demonstrated the younger Kim's unsecured hold on power, or if it was simply a reflection of the continued mourning for Kim Jong-il. Fully answered by an Associated Press dispatch is the question of whether Kim Jong-un will adopt a bellicose stance toward foreign governments as he attempts to assert his own leadership. In the video from state television, the North's new leader said he was determined to go to war against rival nations if a rocket North Korea launched in 2009 was shot down.

The video showed Kim Jong Un shaking hands with officials at a satellite control center after scientists launched a rocket in April 2009 that stoked regional tensions and earned North Korea international sanctions and condemnation.

“I had decided to wage a real war if the enemies shot down” the rocket, Kim Jong Un was quoted as saying. A voice-over described Kim Jong Il as saying his son was in charge of the military’s anti-rocket interception operations at the time.

North Korea has said it successfully sent a satellite into orbit as part of a peaceful bid to develop its space program. U.S. and South Korean officials, however, said no satellite or other object reached orbit, and accused the North of using the launch to test its long-range missile technology.

At the time, Japan had threatened to shoot down any debris from the rocket if the launch went awry. U.S. lawmakers also urged their military to shoot the rocket down.