The last new shotgun i bought was 3 years old at the time of purchase. As said above it is very common if not expected.
There is nothing wrong with it. The gun doesn't degrade over time if stored well (as most gun shops do), and it has not been shot, unless of course proofed if coming from a country that has those laws.
Also who knows how long it has been sitting with a distributor before being ordered by the particular dealer. Especially if it is not a model in high demand.
However in the past new guns could be on the shelves much longer.
I purchased a rifle from a man who bought it in 1959, while the rifle itself has a date of 1950. As well as hearing similar stories of the past from others.
Happy shooting with your new gun!