Little tips about calculating dates.
I needed to find the date of 2010-04-17 minus 200 days. How do you do it in emacs?
Start calendar mode by tying “Alt+x cale Enter”. In calendar mode, the left arrow moves you back. But it also takes a universal argument of n to go back n days. So, type “C-u 200 ←” will put you 200 days back.
When your cursor is in the calender pane, there are these new menus: Scroll, Goto, Holidays, Diary, Sun/Moon. Check them out! I've been using emacs for 12 years, but never realized this!
PS thanks to people on comp.emacs, in particular Jason Rumney.