So let's try an example. Suppose we wanted to find the days between dates. 2013
Janurary 24, and 2013 June 29th. If we were going to do this as a human we might
look at a calendar. I happen to have a calendar handy and thanks to my auntie in
Belfast for sending me the calendar and we could count the days using the
calendar so let's look at the calendar. We have our starting day is January 24
and we might count the days between January 24. How many do we have left in
January. So there would be 1,2, 3, 4, 5, 6, 7 days left in January. So there'd
be seven days in January. Then we have, have all of February, all of February is
28 days. Then we have all of March, 31 days. All of April, 30 days. All of May,
31 days. And then we have June. We don't want to count all of June because we
are stopping on June 29th, so we are going to add 29 days. From June, and if we
sum all those up we should get our answer. And as a human we know how to compute
sums by entering sums into Google, and we get 156.