回复：大内高手们请指教：neither the sun nor its shadow reigned.怎样理解？或整段翻译一下。

That is the day when the sun is orbiting right above the equator, splitting the earth into equal halves.  What the author is trying to express is that when the sun is bathing the northern part of the earth (rules/reigns by sun), then the other half is without sunshine (rules/reigns by shadow).  Of course, there is no shadow on the other half of the earth, only longer distance from the sun and less warmth. Logically, this geographic knowledge is not properly used literally, as result of which, there is quite bit of misunderstanding here.  If it is distracting, regardless of author’s intention, then it should be avoided.