Tweets on a plane calendar! What's not to love? And since every Tweet has a timestamp, it should be pretty easy to feed that data into a Google Calendar (in fact, it's been done). And it's interesting to look at how my patterns have changed since I started using Twitter.
Now this is the kind of thing that Yahoo Pipes is great at—taking data from one service and reshaping it to fit somewhere else. Now if you're a prolific Twitterer, it can take some time to process all that data, so enter your username (no authentication required—this won't work if your updates are private!) below, and start the process. It will be one click to start importing your Tweets into your Google Calendar (note: it may take a few minutes to render all your data. Only works on your last 3,200 updates.). This is set-and-forget, so once you've subscribed, your calendar will update automatically
