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The "Time Gadget" item in the "In The Works" column on the Trello (https://trello.com/c/5z9OI3ON/39-time-gadget) mentions that it will also add extra tweaks to the Sun & Sky gadget to enable it to compute the sun position procedurally.

But the inputs mentioned for this feature are time of year ("date"), time of day ("time"), latitude, and longitude. Time of day and longitude being two separate inputs is redundant - the combination of the effects of those values on sun position is a simple addition. Those inputs should be combined into a single "Longitude + Time of Day" input.

Also, the three inputs - time of year, longitude + time of day, and latitude - that leaves you with aren't quite enough. There should also be an "axial tilt" input, because the effect of axial tilt on sun position doesn't combine with any other input by simple addition.

The four inputs would determine sun position like this, with innermost to outermost referring to how you would set it up if the sun were a sculpt in a nested rotation rig rotating about the scene origin. Positive rotations about an axis are anticlockwise looking along that axis, negative rotations about an axis are clockwise looking along that axis:

1. Start with sun at nadir.
2. Apply time of year as the innermost rotation about the positve z axis - a logic network can increase this value with time for a planet orbiting prograde, and decrease it with time for a planet orbiting retrograde.
3. Apply axial tilt as the second innermost rotation about the positive x axis - a positive value makes time of year 0 the northern winter solstice / southern summer solstice, and a negative value makes time of year 0 the southern winter solstice / northern summer solstice.
4. Apply longitude + time of day as the second outermost rotation about the positive z axis - a logic network can increase this value with time for a planet rotating retrograde decrease it with time for a planet rotating prograde. That mapping of positive changes to retrograde and negative changes to prograde is opposite the mapping for time of year, so an alternative convention would be to apply this as a rotation about the negative z axis.
5. Apply latitude as the outermost rotation about the positive x axis - negative values are northern latitudes and positive values are southern latitudes. Alternatively, apply this as a rotation about the negative x axis to map positive values to northern latitudes and negative values to southern latitudes.