All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
If the moon is seen by day, then it is the moon of the night to come. If this was on the thirtieth day of Shaʻbaan, then one should not fast for the rest of the day because this did not prove the start of the month of Ramadan. If this takes place on the thirtieth day of Ramadan, one should not break his fast because the month of Shawwaal has not yet started, whether it was sighted before or after the sun leaves its meridian. There is no difference among scholars as far as we know concerning this ruling in case the moon was sighted after the sun leaves its meridian. Regarding the case of sighting it before the sun leaves its meridian, this is the opinion of the majority of scholars. Some of them held the view that if it is sighted before the sun leaves its meridian, then it belongs to the previous night and if it is sighted after the sun leaves its meridian, then it belongs to the coming night.
Al-ʻIraaqi said, "If the moon is sighted by day, then it belongs to the coming night. If this takes place on the thirtieth of Shaʻbaan, then they should not fast. If it occurs on the thirtieth of Ramadan, then they should not break their fast whether this happens before or after the sun leaves its meridian." This is the famous opinion of the four schools. It was adopted by ʻUmar, Ibn Masʻood, Ibn ʻUmar, Anas . It was also adopted by Al-Awzaaʻi, Al-Layth Ibn Saʻd and Is-Haaq Ibn Raahawayh . Sufyaan Ath-Thawri, Abu Yoosuf and some Maaliki jurists said that if it is sighted before the sun leaves its meridian, then it belongs to the previous night. This was one of the opinions of Ahmad and it was said by Ibn Hazm Ath-Thaahiri .
If the moon was sighted on the thirtieth day before sunset and disappeared before sunset as well, then this night is the beginning of the month. It is not necessary in this case to sight the moon after sunset because the past month has exhausted its number of days.
The jurists speak about this matter for their difference concerning the day on which the moon was sighted; is it the last day of the previous month or the first day of the coming month? However, the night that follows this day definitely belongs to the new month as we explained above. We mentioned at the beginning of this Fatwa what we view as the preponderant opinion in this difference.
If the moon was sighted on the twenty-ninth day before sunset and was not seen after it, then it seems from the words of the Maaliki scholars that this is enough to prove that this night is the beginning of the month. Nevertheless, Shaafiʻi scholars said that this is not sufficient unless it is sighted after sunset.
Allaah Knows best.