Looks to be ~1.5 years between christening (naming ceremony w/ the bubbly :) / launching, and the commissioning, for these boats anyway. This was just the first time that I had noticed that the commissioning ceremony was happening so far away from the shipyard (my ignorance here).
When the boat is launched there aren't a lot of Navy in sight and the hull is watertight but not much else. Gradually as systems are installed some Navy will show up to accept this or that system. Eventually the Captain shows up to formally accept the key to the door, to meet his crew, either the Blue crew or the Gold crew, and away they go.