The Serapia is a holiday dedicated to Lord Serapis, God of the afterlife, abundance, destiny, miracles, fertility, and healing; who had gained a large following during the Roman Period when His worship spread beyond Egypt.
The Serapia was celebrated, sometimes for numerous days, in the form of festivals complete with processions and feasting. Music from musical instruments such as kitharas and flutes would be filling the ears of those who attended. Philanthropy is also practiced, with bonuses usually given to those who worked under the wealthier individuals who did celebrate the Serapia.
This day is to be celebrated as a feast to Serapis. An offering should also be given to Him, most particularly perfumes and incense.
Abdelwahed, Youssri. “Two Festivals of the God Serapis in Greek Papyri.” Academia.edu. Accessed December 02, 2017. http://www.academia.edu/28855885/Two_Festivals_of_the_God_Serapis_in_Greek_Papyri.
Aristides, Aelius (Aristides, XLV, I8-zo, Keil)