Model 31420E LED alarm clock

The clock changes the time in the middle of the night, I haven't been able to find the answer to this problem. If this has to do with the time zone, how do I change it?

Model 31420E Time Zone:

PROGRAM MENU:

DST/TIMEZONE: Press and hold the WAVE/SET button for 5 seconds and ON and the Time Zone will be flashing. 

DST: Press and release the MINUS button to turn DST indicator ON (if you observe DST) or OFF (if you do not observe DST).

TZ:Press and release the PLUS button to select the Time Zone. The Time Zone will flash in the upper right-hand corner.  E= Eastern Time, C= Central Time, M= Mountain Time and P= Pacific Time. Press and release the WAVE/SET button.

YEAR: The Year will be flashing. Use the PLUS button to increase the number or the MINUS button to decrease the number. Press and release the WAVE/SET button.

MONTH/DATE: The Month and Date will be flashing. Use the PLUS button or the MINUS button to set the Month and Date. Press and release the WAVE/SET button.

TIME: The Time will be flashing. Use the PLUS button to increase the number or the MINUS button to decrease the number. Press and release the WAVE/SET button.

12/24-HOUR and F/C:  12Hr or 24Hr and the Temperature will be flashing.

12/24-HOUR: Press and release the PLUS button to switch between 12-hour or 24-hour time.

F/C: Press and release the MINUS button to switch between Fahrenheit or Celsius. The Temperature will flash in the lower right-hand corner.

Press and release the WAVE/SET button and you are done.  The clock will continue to search for a signal for 10 minutes every 3 hours.