LEAP YEAR

About:

• 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.