Why does Eliezer compare their situation to a dream?

For Eliezer, everything had happened so fast that it seemed impossible..... like a dream.

So many events had taken place in just a few hours that I had completely lost all notion of time. When had we left our homes? And the ghetto? And the train? Only a week ago? One night? One single night?

How long had we been standing in the freezing wind? One hour? A single hour? Sixty minutes?

Surely it was a dream.