By tracking the sun, we can determine the time of local noon (when the sun reaches its zenith, the point at which it is highest in the sky), which can differentiate from the local standardized time by more than an hour, depending on daylight savings time and one's location in the time zone. In the northern hemisphere, the compass bearing of the sun (its azimuth) at local noon in turn determines true south (which is 180˚ opposite from true north, as opposed to magnetic north). Thus, a celestial navigator could use a quadrant and the sun to calibrate a compass.