Occurring on the 14th day of Highgleam, Sunsummit was the Long Gleam solstice of the Common Calendar and the longest day of the year. For much of Commona, the land was lit for 16 hours during Sunsummit, with only 8 hours of night. Many festivals, holidays, and religious observances occurred during this period, especially dedicated towards Thestus and Umera.
Sunsummit was contrasted by Moonsummit, the shortest day of the year.