Explanation:

Saturday is February 29, a date that comes approximately once every four years making 2020 a leap year.

Why have leap years:

• Earth takes close to (not exactly) 365 days and 6 hours to orbit the Sun, which means that the calendar year is about 6 hours shorter than the actual solar year.
• By the end of 4 years, the calendar years will have missed a total of 24 hours, or one full day. To compensate, we have leap years.

Rules and exceptions

• Leap years are always multiples of four — 2016, 2020, 2024 — but a year that is a multiple of four is not always a leap year.
• There are exceptions, such as 1900 and 2100, both multiples of four, yet neither a leap year.
• But again, there are exceptions to such exceptions. For example, 2000 ended with 00 but remained a leap year.

Formula: The formula for leap year in the Gregorian calendar is:

• A year that is a multiple of 4 is a leap year; except:
• A year ending with 00 is not a leap year; except:
• A “00 year” in which 00 is preceded by a multiple of 4 (1600, 2000, 2400 etc) remains a leap year.
• That is why 1900 are 2100 are not leap years, but 2000 is one.