It would depend on the type of opossum that you have. The Virginia Opossum is known to be active during the night. Most opossums can hunt for food at night or they may also be spotted more at night compared to during the daytime. There are also some who are more active during the summer months.
They would hibernate once winter comes. A lot of opossums stay at nests that they have created. The nests are where they would reside during the fall and winter season. By the time that summer rolls around, that is the time when they would search for more food again to stock at their nests.