Bay'a to al-Mu'tadid as heir apparent

al-Tabari mentions the oath of allegiance to Abu al-Abbas as heir apparent, who was given the title al-Mu'tadid bi-Llah. The year is given differently in two reports. ¹

In the account for 278 AH, al-Tabari mentions the oath to Abu al-Abbas as heir apparent in Safar, and his title al-Mu'tadid bi-Llah. ¹ In the account for 279 AH he mentions the deposing of Ja'far al-Mufawwad from the succession and the appointment of al-Mu'tadid in Muharram. ²

al-Suyuti relates that al-Mu'tamid held a general session in 279 AH, and in it he called witnesses that he had deposed his son al-Mufawwad from the succession, and had given the oath to Abu al-Abbas with the title al-Mu'tadid. ⁴

The conflict between the years 278 and 279 stands in the sources, and the museum does not favour either.