@14:20 AD does not mean 'after the death', rather, it is Medieval Latin and means "in the year of the Lord" i.e. the year Jesus was born - according to christians
Ahmad bin Muhammad bin Sa'eed bin Oqda narrated from Muhammad bin al-Mufadhdhal bin Ibraheem bin Qays from al-Hasan bin Ali bin Fadhdhal from Tha’laba bin Maymoon Abu Iss’haq from Eessa bin A’yun that Abu Abdullah as-Sadiq (as) had said:
“The rising of as-Sufyani is an inevitable matter. He will rise in the month of Rajab. It will take, since his rising until his end, fifteen months. He will fight for six months. When he conquers the five districts, he will rule for nine months no more no less.”
Ahmad bin Muhammad bin Sa'eed narrated from Ali bin al-Hasan at-Taymali from al-Abbas bin Aamir bin Rabah ath-Thaqafi from Muhammad bin ar-Rabee’ al-Aqra’ from Hisham bin Salim that Abu Abdullah as-Sadiq (as) had said: “When as-Sufyani conquers the five districts, then you count to him nine months (the period of his rule)” Hisham claimed that the five districts were Damascus, Palestine, Jordan, Homs and Halab.