Imam Abu Abdillah (as) was asked about a group of people who are Fasting in the Month of Ramadhan, so the black cloud overcomes them during the setting of the sun. So, they see it as being night, and some of them break the Fast. Then the clouds move away, so the sun is [still] there.
He (as) said: It is upon those who break, to make up for the Fast of that day. Allah, Mighty and Majestic is saying: Complete the Fast up to the night [Quran 2:187]. So, the one who eats before the entry of the night, so upon him is its making up, because he ate deliberately.
[al Kafi, Volume no. 4]
Divine Treasure 