When was cold war held?

Although the Cold War was an informal war, which was never declared on any specific date and which also was never ended by any formal peace treaty, it can still be dated as running approximately from 1945 to 1990. Until the end of WW II the US and the USSR were formally allies against the Axis Powers (although even then they did not trust each other) so the Cold War could not begin until WW II ended, and then, with the fall of the Berlin Wall and the reunification of Germany in 1990, the last remnant of the Soviet empire ended and the Cold War was over (even though North Korea seems to want to perpetuate it).