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๐ฌ Think about it
Farmers needed a calendar that stayed locked to the seasons, so the year could match planting and harvest. That's the solar calendar — the Gregorian one on your wall. But why does February have an extra day some years? Let's find out.
What is a solar calendar and why are there leap years?
- A solar calendar keeps the year in step with the seasons.
- The Gregorian calendar is a solar calendar of 365 days.
- The Earth takes an extra quarter day each year to orbit the Sun.
- So an extra leap day is added every four years.
Example:
In a leap year (one divisible by four), February has 29 days instead of 28.
๐ก A step further
- Adding a day every four years adds a little too much over time.
- So leap years are skipped every 100 years, like 1700, 1800, 1900.
- But every 400 years a leap year is kept, like 1600 and 2000.
- These corrections keep the calendar matched to the seasons.
๐ก A step further
- The time between successive spring equinoxes is the tropical year.
- The Gregorian calendar is based on the tropical year.
- The time for the same stars to rise at sunset is the sidereal year.
- The sidereal year is longer than the tropical year by about 20 minutes.
Important Points
- A solar calendar keeps the year in step with the seasons.
- The Gregorian calendar has 365 days, with a leap day every four years.
- The tropical year (equinox to equinox) is its basis.
Important Definitions
- Solar calendar — a calendar kept in step with the seasons, like the 365-day Gregorian calendar.
- Leap year — a year with an extra day added (29 February) to adjust for the extra quarter day.
- Tropical year — the time between successive spring equinoxes; the basis of the Gregorian calendar.
- Sidereal year — the time for the same stars to rise again at sunset, about 20 minutes longer than the tropical year.
๐ NCERT Question 10 — If we stopped having
If we stopped leap years, in about how many years would Independence Day fall in winter?
View Answer →
