Do you have a tighter date than that? Technically, the pre-Celts were either (1) Israelites who left Egypt by sea prior to the overland Exodus, or (2) Israelites who left Moses merry band after the overland Exodus but prior to the Assyrian Captivity of the Northern Kingdom ~922 BC. That would be almost 2,000 years before the Vikings discovered America.
However the many different and dispersed Celtic tribes had lots of time between their appearance at the same time and place the Northern Kingdom (Lost Tribes of Israel) appeared in history ~610 BC, and the time of the Vikings.
(For readers unfamiliar with Celtic history, please click on my LostTribe Profile below and check out the 3-MINUTE HISTORY.)