Calculate Leap Years

To calculate if a year is a leap year is easy.

Steps

Start off using the year you want to calculate.
See if it is evenly divisible by 4 (a whole number with no remainder). If it is not, like 1997, it is not a leap year. If it is, like 2012, keep reading.
See if the year is divisible by 100. If a year is divisible by 4, but not 100, like 2012, it is a leap year. If a year is divisible by both 4 and 100, like 2000, keep reading.
See if the year is divisible by 400. If a year is divisible by 100, but not 400, like 1900, then it is not a leap year. If a year is divisible by both, then it is a leap year. So 2000 was indeed a leap year.

Leap years: 1600, 1604, 1608, 1612, 1616...1684, 1688, 1692, 1696, 1704 (no 1700, see why?), 1708, 1712...1792, 1796, 1804 (no 1800), 1808, 1812...1892, 1896, 1904 (no 1900), 1908, 1912...1992, 1996, 2000 (there is a 2000, see why?), 2004, 2008, 2012...2092, 2096, 2104 (no 2100)...2196, 2204...2296, 2304...2396, 2400 (see why?), 2404...etc.
Any year divisible by "4" is a leap year. 1 year is ‘365 days + 6 hours', which is the same as 365 and 1/4 days. Every 4 years, the 6 hours become one day (6X4=24 hours) and the reason why we have extra day in February.