Imam Malik (may Allah have mercy on him) was informed that during the time of Sayyiduna Uthman ibn Affan (may Allah be pleased with him), the moon was sighted in the afternoon, but he did not break his fast until evening came and the sun had set.
Imam Malik, may Allah have mercy on him, said: Whoever alone sees the crescent of Ramadan should fast, because it is not permissible for him to break the fast when he knows that this day is of Ramadan. And whoever alone sees the crescent of Shawwal should not break the fast, because people will accuse him, saying that among us, the person who is not trustworthy does not fast. And when the crescent becomes apparent to the people, he should say that he had seen the crescent. And whoever sees the crescent of Shawwal during the day should not break the fast, rather he should complete the fast, because that crescent is for the coming night.
Imam Malik, may Allah have mercy on him, said: If people fasted on the day of Eid thinking that it was a day of Ramadan, and then a trustworthy person came and said that the moon had been sighted a day before you began fasting and that this day is the thirty-first, then they should break their fast as soon as they receive this news. However, if the time of decline (zawal) has passed, then they should not perform the Eid prayer.
Hadith Referenceموطا امام مالك رواية يحييٰ / كتاب الصيام / 580