Daniel 8:1 (ESV)

1 In the third year of the reign of King Belshazzar a vision appeared to me, Daniel, after that which appeared to me at the first.

Two years after the previous dream, the Lord again comes to Daniel. Once more Daniel sees things concerning the future. We are now in the third year, 547 BC, of King Belshazzar. What Daniel sees this time is a further elaboration of what he sees in Daniel 7, specifically the details of the second and third beasts.