Is the intention to fast Ramadan required at night, or is it permissible to make it during the day?

The intention to fast Ramadan must be made before Fajr. If one learns during the day that it is a day of Ramadan and then intends to fast, they must abstain [from food and drink] and make up that day, due to the Prophet's (peace be upon him) saying: "Whoever does not gather the intention to fast before Fajr, there is no fast for him." As for voluntary fasts, the intention for them may be made during the day, provided one has not done anything that breaks the fast after Fajr, based on the action of the Prophet (peace be upon him).