How can I calculate the unit vector to the sun for specific time relative to observer position, given with lat:lon coordinates, considering Y+ axis directed to North, X+ axis directed to East and Z+ directed as radius vector to observer position from center of the Earth?
UPDATE: Answering to hardmath's comment, the Earth may be considered as ideal sphere, Earth's orbit may be considered as ideal circle and Earth's axis tilt may be considered as $\mathcal E = 23.4°$.
P.S.: Sorry for bad English.