It is narrated from Khalid bin Aslam (may Allah have mercy on him) that Umar bin Khattab (may Allah be pleased with him) broke his fast on a cloudy day in Ramadan, thinking that perhaps evening had come and the sun had set. A man came and said, "O Commander of the Faithful! The sun has risen," (meaning it had not yet set). So Umar (may Allah be pleased with him) said: "This matter is easy."
Hadith Referenceمسند الإمام الشافعي / كتاب الصيام / 657
Hadith Takhrijاسناده صحیح اخرجه مالك في الموطاء الصيام، باب ماجاء في قضاء رمضان والكفارات والبيقي 117/4 ۔ وفي المعرفة السنن والآثار له، رقم : (2473)۔
Imam Shafi’i, may Allah have mercy on him, said: Whoever vomits intentionally while fasting, it is obligatory upon him to make up the fast. And whoever vomits unintentionally (i.e., does not do so deliberately), then making up the fast is not obligatory upon him.
Hadith Referenceمسند الإمام الشافعي / كتاب الصيام / 658
Hadith Takhrijاسناده صحیح اخرجه البيهقى 219/4 ۔ وفى المعرفة السنن والآثار له ، رقم : (2475)
It is narrated from Abu Salamah (may Allah have mercy on him) that he heard from Aisha (may Allah be pleased with her) who said: I used to have to make up the missed fasts of Ramadan, but I would not have the ability to do so before Sha'ban. (That is, I would make them up in Sha'ban.)
Hadith Referenceمسند الإمام الشافعي / كتاب الصيام / 660
Hadith Takhrijاخرجه البخاري، الصوم، باب متى يقضى قضاء رمضان (1950) ۔ ومسلم، الصيام، باب جواز تأخیر قضاء رمضان مالم .... الخ (1146)۔