As the result of feedback and comments, I made some minor adjustments to the presentation on the Watchtower's method for calculating 1919. These adjustments are so minor that I doubt whether most people will notice them. I guess I am a bit of a pedant.
Anyway, the URLs for the touched-up files are:
For the PowerPoint Show: http://www.jwstudies.com/Appointed_in_1919_version_2.ppsx
For the PDF file: http://www.jwstudies.com/Appointed_in_1919_version_2.pdf