Chrono Machine is a simple app that provides some information about dates. There are five different modes: Day, Years, Christmas, Epiphany and Easter. You can access all the modes from the main window. Some of them require you to input a date that the app uses to calculate which day a certain even fell on.
The two most interesting modes are Day and Years. The first one can calculate what weekday a certain date fell on. This is a nice tool for when you want to know what day your birthday was or which day a specific event happened on. All you need to do is input the century, month, day and year, and the application will tell you what day it was. The Years mode does something similar. You select a month, day and date and the application you will tell you in which years that was the date. It is kind of an inverse mode for the "Day" mode.
The rest of the modes deal with dates on which Christmas and Easter was celebrated, as well as epiphany years. Those are pretty self-explanatory. In short, this is a nice tool that can quickly calculate dates for you.