## Questions

- What is a leap year?
- How often do leap years occur?
- On what date is Leap Day observed in a leap year?
- Which calendar introduced the concept of leap years: the Julian calendar or the Gregorian calendar?
- According to the Gregorian calendar, which years are leap years?
- What is the mathematical rule used to determine if a year is a leap year or not?
- Who introduced the concept of leap years into the calendar system?
- In what year did Pope Gregory XIII introduce the Gregorian calendar, which refined the leap year system?
- In which years were the Summer Olympics held avoiding leap years?
- Why are some years divisible by 100 not considered leap years unless they are also divisible by 400?

## Answers

- A leap year is a year that contains an additional day, known as Leap Day.
- Leap years occur every four years.
- Leap Day is observed on February 29th in a leap year.
- The concept of leap years was introduced in the Julian calendar.
- According to the Gregorian calendar, years divisible by 4 are leap years, except for years that are divisible by 100 but not by 400.
- The leap year rule is:
- If the year is evenly divisible by 4, it is a leap year.
- However, if the year is evenly divisible by 100, it is not a leap year.
- Unless the year is also evenly divisible by 400, then it is still a leap year.

- The concept of leap years was introduced by Julius Caesar and further refined by Pope Gregory XIII.
- Pope Gregory XIII introduced the Gregorian calendar in 1582.
- Summer Olympics are typically held in non-leap years, except for 1900 and 2021.
- Years divisible by 100 are not leap years unless they are also divisible by 400 to accommodate for inaccuracies in the calendar system.