Topics Covered: Important Geophysical phenomena such as earthquakes, Tsunami, Volcanic activity, cyclone etc., geographical features and their location- changes in critical geographical features (including water-bodies and ice-caps) and in flora and fauna and the effects of such changes.
Why we have leap years?
What to study?
For Prelims and Mains: What is leap year, when and why it is considered?
Context: The year 2020 is a ‘leap year’, meaning the month of February will have 29 days instead of 28, and the total number of days will be 366 instead of 365. This was also the case in 2016, and 2024 will again be a leap year.
Why do we have leap years?
- The time required by the Earth to complete its orbit around the Sun is approximately 365.242 days. But years are usually only 365 days.
- To adjust for the extra 0.242 days in the orbital period, which becomes almost one full day in four years, the calendar adds an extra day once every four years.
- This approximates the time to 365.25 days, which is close to the actual 365.242 days.
In the Gregorian calendar, a century year (a year ending with 00) is not a leap year, even though it is a multiple of 4. Thus, the year 2100 will not be a leap year. To ensure that, some century years remain leap years. In the Gregorian calendar, leap years include those century years which are exactly divisible by 400. Thus, 2000 remained a leap year even though it ended with 00.
Sources: Indian Express.