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.
The only metric unit of time is the second. all the other ones are customary units that are geared towards living on Planet Earth. There was a movement for decimal time at one point, but it never really took off. Given that the length of a day changes, I don't see how it would remain stable either. Which is something that SI units try very hard to make sure doesn't happen.