How to set your own date for the end of the world

Have you ever wondered how Harold Camping and his followers figure out the date for the end of the world? One of Camping's closest followers provides this link: Numbers in the Bible. I know, that's not that impressive. Here's what is: they also have developed a computer program to do their Bible math:

Bible Calculator: The Bible Calculator is a computer tool for researching numbers and time intervals found in God's Word, the Bible

Bible Calculator (Java)

I wonder if any of the people who developed this program had anything to do with Windows Vista.