It's probably a UTC timing problem. Since the data is on a web server which can be accessed and updated by web browsers from throughout the world, all times are stored on the Method server in UTC, which at this time of year is 5 hours ahead for someone in an Eastern time zone, and 6 hours ahead for someone in the Central time zone.
So you enter 2009-01-20, and the server takes this as 2009-01-20 12:00 AM UTC. When you view this in a browser, we detect your central time zone and display it 6 hours earlier, so 2009-01-19 6:00 PM. So it is viewed as Jan 19th.
What you need to do is pass over 2009-01-20 6:00 AM, so that it comes back to your browser as 2009-01-20.
Hope that makes sense.