2006 AMC 10B 第 16 题

Count the days from one Leap Day to the next: $3\cdot365+366$

That total is $1461\equiv 5\pmod 7,$ so each $4$-year cycle advances the weekday by $5$

From one Leap Day to the next is $3\cdot365+366=1461$ days, and $1461\equiv 5\pmod 7.$

Over the four cycles from $2004$ to $2020,$ the weekday advances $4\cdot5=20\equiv 6\pmod 7,$ that is, $6$ days forward, which is one day back from Sunday.

So Leap Day $2020$ falls on a Saturday.

Thus, the correct answer is E.