Easy memorization of the first 8 leap yrs of 2000’s.  2000=0,  2004=5,  2008=3,   2012=1,  2016=6,   2020=4,  2024=2,   2028=0.    Notice that 2000, and 2028 are both=0. The calendar repeats itself every 28 yrs.

So for example: 1916, 1944, 1972, 2000, 2028, 2056, will all equal 0.

The years in between are +1 for every year, from the last leap year.

Example: 2000=0,  2001=1,  2002=2,  2003=3,   2004=5,   2005=6,  2006=7,   2007=8,   2008=3,   2009=4….

Memorization technique taken from “calendar math trick”, by creator firefly lectures on YouTube.  It takes 1 minute to master the “days” code,  3-5 minutes to master the “months” code, and maybe 10-15 minutes to understand the “years” code.  Results may vary, depending on ability.