Sun light is a directional light whose direction can be controlled by time, latitude, and longitude, or alternately just by altitude and azimuth.
This can be used to analyse solar orientation for buildings.
To control by time and location, set MODE>POSITION and optionally also MODE>INTENSITY for it to get brighter and darker
Setting NORTH and UP are critical to getting it right. The 3 input boxes are assumed to be X Y Z, so if you want the Y AXIS to point to NORTH, then enter 0 1 0. Optionally 0 -1 0 would NORTH pointing in the opposite direction along the Y AXIS. Any combination can be done.
UP seems to work the same way, so 0 0 1 makes the Z axis point to North.
The LATITUDE for the southern hemisphere needs to be negative (-35lat 149long works for Canberra Australia)
The longitude seems to work in conjunction with the time from your computer. For Canberra Australia in summer, time must be set to 1pm to get sun directly north as there is daylight saving of one hour in summer.