“I started by asking other editors and reporters what important dates in history they thought should be included. Then I added my own list. Surprisingly, that still only made up about 75 historic dates. So I started consulting history books. That brought me up to about 100 or 125. I knew then I could really start my research of actual pages, because I knew that was going to turn up still more pages. And it did. I eventually worked from a list of about 200 dates, and gradually edited them down to 150 that I felt were both historically and culturally noteworthy.”