Armageddon is the situation of the nations against God.
The entire 3 1/2 years of tribulation the nations are against God, because it is at the beginning of that time period Jesus takes the throne in heaven and the kingdom begins. The entire 3 1/2 years of tribulation the Devil empowers the UN to be the dominant world power in opposition to Christ's rule. The 3 1/2 years of the great tribulation is the time spoken of in Psalms when Christ rules for a little while amongst his enemies. The dream image vision in Daniel shows the kingdom begins during that time the UN is dominant world power. The feet of that vision are the UN. The other visions in Daniel also show the UN is against the holy ones during that 3 1/2 year time.
Armageddon is the entire situation of the nations during the 3 1/2 years of tribulation. Then the time of the nations is cut short, so that the holy ones will be saved. That is the appointed times of the nations: the 3 1/2 years of great tribulation, aka Armageddon.
https://www.youtube.com/watch?v=Z0GFRcFm-aY