The nominal 0 deg C voltage and the temperature coefficient are
given in the datasheet with their respective tolerances.
The nominal 0 deg C voltage is specified to be 986mV +/- 5% max
error. So, the 0 deg C voltage of the temperature sensor can vary
worst case almost +/- 50mV from device-to-device. This is roughly
equivalent to +/- 14C. Note, that this variance is primarily
device-to-device dependent, so that with proper calibration on an
individual device, very accurate absolute temperature can be
obtained with the full resolution of the ADC12.