Did you know a year was 400 days long just a couple of years ago. Like 400 million years ago, to be less inexact and more precise at the same time:
Though incredibly long by human standards, a million years is still relatively short by geological standards. Back in the Devonian period, some 400 million years ago, days would have been only about 21½ hours long. Given that the year (the time it takes the Earth to revolve around the sun) has not changed appreciably, there would have been slightly over 400 days to the year back in the Devonian.