What is the ruling on writing the name of the deceased and the date of their death—in both Hijri and Gregorian calendars—on a small plaque placed on the grave for identification purposes? And does this violate the prohibition against writing on graves?

A Muslim must obey the commands of the Prophet (peace be upon him) and avoid what he has forbidden. The Prophet forbade plastering graves and writing on them. It is permissible to mark a grave with a stone or a piece of wood. As for writing, the majority of scholars consider it disliked, while the Hanafis and Ibn Hazm permitted it. Some scholars permitted it when there is a need to identify the deceased, by analogy with marking it with a stone. The benefit of knowing the deceased is for their family to greet them and supplicate for them.