I wanted to make a Vim advent calendar, but I don't think I'll have time now. I found Bram Moolenaar's 2014 calendar, which can be folded to sit on a desk and has the Vim logo and charity information.
It is available in English and Dutch. You can find the PDF files on my website: http://moolenaar.net/#Calendar
If you are doing your Christmas shopping on Amazon, please consider using the links on this page: http://www.iccf.nl/click1.html A percentage of the sales will go to Vim's charity, helping children in Uganda, and it doesn't cost you anything.
If you're looking for a calendar in Vim, you could type
:r! cal. The
cal command is a BSD general command that you may have installed depending on your operating system.
December 2013 Su Mo Tu We Th Fr Sa 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
Alternatively, check out something like calendar.vim, which displays calendars in split windows.