For example,
60 seconds = 1 minute
60 minutes = 1 hour
24 hours = 1 day
7 day = 1 week
29-31 days = Month (approx.)
365/366 days = year
It’s like for the imperial measurement of distance, where 1 mile = 5280 feet…
Edit: just to clarify, I’m more or less keen towards any consistent, decimal-based measurement systems like base-10 or base-12.
Worth emphasizing that the year began in March – December means the 10th month because it was the 10th month, even after January/February were added