And We have made the night and the day (such as they became) two signs, (in a way that) We obliterated the sign of the night (- darkness of ignorance and disbelief) and We displayed the sign of the day as sight - giving that you may seek the bounty of your Lord and that you may learn (from the alternation of night and day) the computation of years and (the science of) all sorts of counting and measuring. We have clearly explained every thing in detail.