This model has an "atomic" clock correct? Around midnight each night it will try to receive the WWVB signal and set the time and date to what it says. If you don't have the time zone set correctly, then you will get problems like this. When it happens again, instead of manually setting the time and date, adjust the time zone setting until the time and date are correct. After that, they should stay that way. Also, set daylight savings to on if you are in an area that observes daylight savings when it is active (even though it is not active right now).