This date stays the same but it is usually close to the Buddhist festival of the hungry ghosts. They came to the tombs of the deceased, with offerings, performing rituals, specifically "fumigations" - producing fumes - smoke.

The ceremonies were often followed by a funerary meal

This is followed on the 19th August with the procession of Heru to Neith and on the 20th August with the Festival of Tehuti (Thoth) marking the occasion on which Tehuti (Thoth) ordered the healing of the eye of Heru (Horus). 

They came to the tombs of the deceased, with offerings, performing rituals, specifically "fumigations" - producing fumes - smoke. I am assuming this is also the origin of Ghost Day.