I've had some thought on this. The issue that I see with auto-focusing is people who use backspace to go back in the browser. If I steal focus then they're just stuck there, mashing on backspace.

As a compromise I implemented arrow key functionality. The down arrow focuses the input field when you're on the Daily tab. The left and right keys also scroll between days/months. I realize that at this point there is absolutely no indication of those features on the site, so consider it an Easter Egg for now. :)