Uh... I was actually thinking about something VERY similar yesterday. That is why this is so very funny to me. I was trying to see how many month/day sequences add up to ten.
ie. 1/9 => 1+9=10, 1/18 => 1+1+8=10, 1/27=> 1+2+7=10, 2/8 => 2+8=10, 2/26 => 2+2+6=10, and so on.
The last possible date on the calendar would be 12/25.
Oddly, everyone in my immediate (me, wife and kids) family has a "10 sum" birthday.