In Revelation 20:2, for how long was the dragon bound?

Answer: A thousand years

An angel came down with the key to the Abyss and a great chain, seized the dragon, and bound him for a thousand years.

“Then I saw an angel coming down from heaven with the key to the Abyss, holding in his hand a great chain. He seized the dragon, that ancient serpent who is the devil and Satan, and bound him for a thousand years.”— Revelation 20:1-2 (BSB)