伊斯兰历从先知穆罕默德从麦加迁徙到麦地那的那一年开始计算。

The Islamic calendar starts from the year of the ___Hijrah, when Prophet Muhammad migrated from Mecca to Medina.

先知穆罕默德从麦加迁徙到麦地那标志着伊斯兰历的开始。

The Prophet Muhammad's ___hijrah from Mecca to Medina marked the beginning of the Islamic calendar.