Twistory takes a tweet timeline and brings it together with your calendar after it indexes that stream. There is no authentication necessary, it will index any public page and give an output in Google calendar format, iCal and for anything that supports webcal. So importing the data itself is quite easy. What you get on the site when entering the Twitter account is a couple quick graphs, such as my example here:
The tweets from the account you are gathering the data and feed are shown down the left and the feed links are at the top of the page. Once it is imported you get all the tweets placed on the calendar and are even to do time tracking by starting and closing tweets with what you are doing with the t and /t marks. The end result is a good way to map out times when someone tweets as well as how often.