Are both reading temps in the tent? Then one is not correct I would guess...a bit more info would help...like what is your regular gauge? Have either been dropped and or stored in the junk drawer where they are jostled around? Try this with the digital to calibrate it, Fill a glass with crushed ice. Add a little clean water until the glass is full and stir. Wait for about three minutes before inserting the sensor on the thermometer into the ice-filled water. Wait for about thirty seconds and check that the thermometer reads 32°F. If it does, then it is accurate, but if not, it requires calibration.