I think that one of the best uses of the term "night" in Wiesel's work would have to be upon his entrance into Auschwitz. Wiesel's reflection about what that first "night" was like is profound:
Never shall I forget that night, the first night in camp, which has turned my life into one long night, seven times cursed and seven times sealed.
The events that surround this word helps to confirm that the Holocaust's terror is one that happens both outside the victim and inside them, as well. Eliezer's first entrance into Auschwitz- Birkenau was filled with horrific images that ended up cementing themselves into the mindset of the subjective. The chimneys, the fires from the crematoriums, the children dying, and the break up of his family in an instant where mother and sister was sent to one side and father and son sent to another. This "night" was one where darkness shrouded him. The use of "night" is powerful here because this particular setting is a "nightmare," one from which there can be no alleviation or waking up. The lack of vision in "night" is especially poignant when one considers that this becomes the final moment he sees his mother and his sister. The shroud of darkness that must have overcome at this moment, an instant where Eliezer never understood that separation would mean permanent loss, but rather one that prevented him from seeing his whole family again.
On the subjective level, the use of "night" helps to bring forth the idea that there is a certain recurring nightmare that happens in the realm of the subjective in terms of life post- Holocaust. It is this particular idea that helps to bring out the psychological horror of the Holocaust for those who had to survive it. This survival is a nightmare, one where the redemption of dawn is missing and one where the feeling of living in darkness is almost permanent. The use of "night" is brought to an emotional crescendo with the idea of "my life into one long night." This helps to confirm the idea that the true horror of the Holocaust is not experiencing what happened, but lives the psyche of the survivors where there is a sense of continual and constant return to those initial moments of pain, those elements where pain is inescapable, and where "night" is a realm of darkness without sleep and without dawn.