Mitch Kapor's Weblog: Chandler's Schedule "Software, like construction projects, is typically late, sometimes very, very late. It typically takes longer and is much harder than any estimates. There are, of course exceptions, like the original version of Lotus 1-2-3, which shipped exactly on time, and there tend to be exceptional reasons why. In the case of 1-2-3, it was implemented almost entirely by one person, Jonathan Sachs, and it was the fifth time Jon had implemented a spreadsheet. Not only did he know what he was doing, but he had enough experience to accurately estimate how long each part of the coding would take. This was one of the keys. The other was that we had a relatively precise idea of the feature set going into the product. In other words, we both knew what work had to be done, and how long each piece would take. It was possible to roll up the schedule from the bottom up."