This was the first explanation that I immediately memorised. Thank you for sharing. I got quite a few right, but as I experimented I failed on February 7th 2032. My math was:

    Years since 2012 is 20
    Leap years is 20/4 = 5
    Magic month number = 4
    Date is 7
    (20 + 5 + 4 + 7) % 7 = 1

So I was expecting Sunday, but the answer is Saturday. After some thought I realised: 2032 is a leap year and the chosen date is before February 29th. In those cases (on or before that day), it is necessary to subtract 1.