[3rd update: Dec. 26th, 2013]
Every year for around 15 years I have been preparing an Uposatha Calendar for the coming year, which shows the dates the Pātimokkha is held.
This started off as a calendar for monks in Sri Lanka, but after leaving that country in 2008 it seemed worthwhile to extend it to show the dates in the various main traditions: Sri Lankan, Thai and Burmese.
I include here a pdf for printing, and also image files for quick viewing.
to calculate monastic dawn and midday anywhere in the world
and get a full year chart for your area, see this page.