First of all, we would like to stress that all fasting people should do their best to make sure when exactly sunset takes place and night draws near. One is to break the fast only when one is sure that the sun has set. Allah Almighty says [So keep your duty to Allah as best as you can] (At-Taghbun 64:16).
The eminent Muslim scholar Sheikh Yusuf Al-Qaradawi, states the following: According to the famous view of the well-known juristic madhabs, if some people have sahur in Ramadan thinking that it is still night and then discover that the sahur or part of it took place after the break of dawn; or if they break the fast before sunset and then realize that the sun has not set yet, the fast of that day has been invalidated, but they still have to abstain from food for the rest of the day and make up for the fast later. They are also not to be regarded sinful for this, since they did it by mistake.
However, Abu Muhammad ibnHazm maintains that the people’s fasting in both cases is still valid, as they did it unintentionally, thinking themselves in a period of non-fasting. In these cases they are like those who have eaten or drunk during the day of Ramadan in forgetfulness; both types have imagined that they are not fasting. Almighty Allah says [And there is no sin for you in the mistakes that ye make unintentionally, but what your hearts purpose (that will be a sin for you).Allah is Forgiving, Merciful] (Al-Ahzab 33:5). The Prophet (peace and blessings be upon him) also said, “Allah will not hold anyone of this nation responsible for what is done in error, forgetfulness, or under coercion” (Al-Bukhari).
IbnHazm, furthermore, said that this is the viewpoint of the majority of predecessors and reported that “The people broke their fast during the time of `Umaribn Al-Khattab. A big pot was brought from Hafsah’s house and the people drank. Then the sun appeared from behind the clouds and this distressed the people. They said, ‘We have to make up this day.’ ` Umar wondered, ‘Why? By Allah, we have not involved ourselves in any sin.'”
Mujahidalso said that those who have eaten after dawn time, thinking that it has not broken yet, are not required to make up for that day, as Almighty Allah says [Eat and drink until the white thread becometh distinct to you from the black thread of the dawn] (Al-Baqarah 2:187). A similar opinion was also reported to have been held by Al-Hakamibn `Utaibah, Al-Hasan Al-Basri, JabiribnZaid, `Atta‘ ibnRabah, `UrwaibnAz-Zubair, and Dawud, the famous Zahiri follower.
In my opinion, the evidence cited by IbnHazm is strong, especially in the case of the legally responsible people who have sahur after the break of dawn, for the Qur’an permits eating, drinking, and making love to one’s spouse until it becomes clear to one that the dawn is breaking. And for those who take sahur thinking that it is still night, it is not yet certainly clear for them that the dawn is breaking.
Hence, I see that those who observe fast are to do their best to make sure exactly when sunset takes place and night draws near. If they are certain that the sun has set and consequently break their fast, then they discover that it has not set yet, I believe they are not blameworthy in this case, as Allah Almighty says [So keep your duty to Allah as best as you can] (At-Taghbun 64:16). That is also why `Umar said, as quoted above, “By Allah, we have not involved ourselves in any sin.” Parallel to this is the case when people stand in prayer directing their face toward the qiblah according to their discretion, but later they discover that they had turned their face to another direction; in such case, their prayer is still valid, as Allah Almighty says:[whithersoever ye turn, there is the presence of Allah] (Al-Baqarah 2:115).