Only us Freelancer Crack-whores.
As to the question of the calendar, well I haven't seen a 13 month one around. Someone compiled it to the old Celtic Year perhaps? (That one followed the Lunar cycles with Samhain/Halloween as the new year) Personally I use a nice little thing that I found in the cover of an old almanac - it lists all of the years's days along with the dates and allows for the shifting cycle to calculate what a specific day (IE:Dec 17th) will be in whatever year you select. Pity that it doesn't include lunar cycles and celestial events like eclipses and suchlke. hmmm, maybe there are some advantages to using a computer program after all...