A close reading of two poetical sources provides new data on the reforms of the fiscal schedule of the Abbasid state in the ninth century. This paper reconstructs the calendrical complications in those Abbasid regions that followed Iranian administrative tradition and its solar calendar without intercalations. Two reforms were issued under al-Mutawakkil and al-Muʿtaḍid to correct the fiscal schedule of these regions. A panegyric by al-Buḥturī allows us to confirm and contextualize al-Mutawakkil’s reform in the final years of his caliphate. A few verses by Ibn al-Muʿtazz give a significant description of the close connection between al-Muʿtaḍid’s reform of the Iranian New-Year’s day and the construction of his public figure.