Units of time include seconds, minutes, hours, days, weeks, months and years. Standard conversions are that 1000 milliseconds equal 1 second, 60 seconds equal 1 minute, 60 minutes equal 1 hour, 24 hours equal 1 day, 7 days equal 1 week, months vary between 28-31 days, and 365 or 366 days equal 1 year composed of 12 months. Larger units are that 10 years equal 1 decade, 100 years equal 1 century, and 1000 years equal 1 millennium.