Thirty Days Hath September,
April, June, and November.
All the rest have thirty-one,
... yadda yadda something about February
I don't know about you, but that grade school rhyme helps me remember which months have how many days. On the occasion that I don't remember that, I'll consult my wall or desk calendar. If those are not within reach, I'll open Outlook or double click on the time in the system tray to get a calendar. But for some, such as Dewayne Christensen's colleague, a poem, paper calendar, or virtual control simply wont do. They'll find the last day of a known month programmatically, such as in this case of determining the lastDay of December ...
Actually, this does have the added benefit of flexibility. When the number of days in December change, this app sure won't break. I don't think I'm alone in remembering how much of a complete pain in the ass it was to refactor our applications when we had to migrate to the Julian Calendar back in 45 BCE.