What is meant by making the intention at night

Question : This questioner says: Honorable Shaykh, what is meant by making the intention at night?

Answer : Praise be to Allah, Lord of the worlds, and I send prayers and peace upon our Prophet Muhammad, the seal of the Prophets, and upon his family and his Companions, and upon those who follow them in excellence until the Day of Judgment. What is meant by making the intention at night is that a person intends to fast before the dawn breaks, even if the fast does not occur for him until a moment before the dawn. It is not meant that he sleeps having already made the intention. Based on this, if a person does not know that the month has entered until a quarter of an hour, five minutes, or one minute before the dawn breaks, and then he makes the intention, his fast for that day is valid. However, if he makes the intention during the day, and the fast is obligatory, it does not suffice for him, because the one who makes the intention during the day has missed part of the day.
As for if it is a voluntary fast, he is rewarded from the time of the intention until the setting of the sun, on the condition that it is not a single, isolated act.