Pre-reform issues, Arab-Sasanian. Ubaydallah b. Ziyad. AH 54-64 / AD 673-683. AR Drachm (31.1mm, 4.14 g, 4h). DA (Darabjird) mint. Dated YE 46 = AH 58 (AD 677/8). Obverse margin: – /
bism allah / – / – / Reverse margin: GM monogram at 11:30h. Malek,
Arab-Sasanian 410-11; SICA 1, 248; Album 12. Near EF.
Most Islamic silver mints had adopted Islamic Hijri dating by the time of ‘Ubaydallah b. Ziyad’s governorship. Darabjird was one of the few which continued to use Yazdigerd Era dates, in which years were counted from the accession of the long-dead Sasanian king, Yazdigerd III. This was a solar calendar with a year of 365 days, while the Hijri calendar is a lunar system with a slightly shorter year of (usually) 354 days. Why the district of Darabjird should have continued to use the older Persian calendar after other parts of Iran had abandoned it is unclear, and having two different dating systems on an otherwise consistent coinage must have been inconvenient and confusing.
The answer may be connected with how taxes were connected in the region. Solar months remain synchronised with the seasons, and so taxes levied after harvest would always fall due in the same month of a solar calendar. But months in a lunar calendar gradually fall earlier relative to the seasons, so levying taxes in a given lunar month would have meant that these fell due before harvest. Traditionally, the caliph ‘Umar b. al-Khattab is reported to have appreciated this problem, and to have allowed the Persian calendar to be reintroduced to facilitate tax collection.
