It is different from the fast of Ramadan; for it is considered a fast of Ramadan, and the reason for the difference is that each of the two times, although it is determined for fasting, the fasting of Ramadan is determined by the designation of the one who has absolute authority, which is Allah, the Exalted. Thus, the determination is established absolutely, which manifests in the right to annul other fasts. The specified vow is determined by the designation of one who has limited authority, which is the servant, so its determination appears in what he has specified for himself when he intends to fast a voluntary fast rather than the obligatory ones that are the rights of Allah, the Glorious and Majestic, at these times. Therefore, the times remain a place for obligations, and if he intends another obligation, it is valid, as mentioned in Bada'i al-Sana'i 2: 84, Sharh al-Waqaya p. 234, and Tanwir al-Absar and al-Durr al-Mukhtar 2: 86.