after hijrah

A.H.means After Hijrah (Migration of Prophet Muhammad (P) and his supporters from Mecca to Medina.
). It is the reference used in the Islamic calender, instead of A.D. which is used in the Christian calender.

AH = Anno Hegirae, the Muslim era. The Islamic calendar is entirely lunar, and unlike most other lunar calendars, is not adjusted to keep in step with the solar year.