Science · 6 pages · 12 min
How leap years keep the calendar with the seasons
Leap days patch the fraction so calendar dates stay with the seasons.
When the purchase is complete, return to the original window. It will refresh.
From the opening
A leap year inserts an extra day so the calendar stays lined up with the seasons. The tropical year, the cycle from equinox to matching equinox, is not a whole number of days, and a stack of plain 365-day years would drift through the seasons. The opening covers why 365 days falls short, the four-year rule and its skip, and seasons versus a star year.
The rest of the brief — the later sections and the reading notes — opens after Stripe confirms payment.
Inside
- Why 365 days falls short
- The four-year rule and its skip
- Seasons versus a star year
- Why leap seconds are different
- Where the idea stops applying
- A distinction worth keeping
Sources
- The Gregorian calendar reform
- The tropical year measured from the equinox