Days, weeks, months, years — time at the human scale.
Quick check
How many days are in a non-leap year?
Nested chunks of time
The calendar stacks units inside units: 7 days make a week, about 4 weeks make a month, 12 months make a year. A year is really one trip of Earth around the Sun — roughly 365.25 days, which is why we need leap years.
The calendar most of the world uses is the Gregorian calendar, introduced in 1582. It tweaked the older Julian calendar's leap-year rule to keep the seasons from drifting.
Recap
- 1 week = 7 days; 1 year = 12 months ≈ 365.25 days.
- A leap year has 366 days (extra Feb 29).
- The year length is set by Earth's orbit, not by anyone's choice.
Conversions
- 1 week = 7 days
- 1 year = 12 months ≈ 365.25 days
- 1 leap year = 366 days