If the time changes or is off by an hour or more:

1. Check to make sure you have selected your proper time zone.
2. If you observe Daylight Saving Time, make sure that DST is always turned ON.
3. Make sure you are using recommended batteries.
4. If the unit is atomic it will automatically correct itself with the date and time once it picks up the atomic signal. Try moving the unit to a window facing Colorado overnight (signal is better at night) so it can gain a strong connection. If it continues to change, you may want to relocate the unit to a different location in your home. 

For more information about specific timekeeping technologies, please review the articles below:

Atomic Clock Technology

Intelli-Time® Clock Technology