Chardin had noted the use of two dif­fe­rent calen­dars in Persia, lunar and solar. Montesquieu in this novel uses lunar months, no doubt because they “are the com­mon months of all Muhammadams, for both spi­ri­tual and civil pur­po­ses” (Chardin, V, 116-118). But he makes them cor­res­pond to the months of the European solar calen­dar, as Robert Shackleton sho­wed in a defi­ni­tive arti­cle on the sub­ject.1 We the­re­fore repro­duce the table which Shackleton drew up, adding the names used by Chardin.

Designations of Persian months
Names in Persian Letters Names as they appear in Chardin
Zilcadé January Zirkadé
Zilhagé February Zilhajé
Maharram March Maharram
Saphar April Safar or Sefer
Rebiab I May Rebiah I
Rebiab II June Rebiah II
Gemmadi I July Gemadi I
Gemmadi II August Gemadi II
Rhegeb September Regeb or Rajeb
Chahban October Chahban
Rhamazan November Rhamazan
Chalval December Cheval

Robert Shackleton, “The Moslem chronology of the Lettres persanes”, French Studies, no. 8, 1954, p. 17-27 ; reprinted in R. Shackleton, Essays on Montesquieu and on the Enlightenment (Oxford : Voltaire Foundation, 1988), p. 73-83.