This is basically all Revenge of the Sith spoilers, so read on at your own peril.
The second to last scene of Revenge of the Sith features Darth Vader and the Emperor overseeing the construction of the first Death Star. Several things imply this takes place some time after the film's main narrative.
- The Star Destroyers have been remodeled.
- The Republic Navy has transitioned into the Imperial Navy and the officers have received new uniforms.
- Vader has gotten used to his armor and the Imperial officers have gotten used to Vader.
How much time has passed?
Edit: Some people are claiming my question is a duplicate of this one. However, all the linked question's answers state is that the Death Star was in construction during the Clone Wars. They do not mention any of the clues that this scene takes place at a later date, nor do they state when the scene actually takes place.