A school holds its sports day on the circled date. Its annual function is exactly 100 days later. When is the annual function?

20 July 2026 is a Monday. $100=14\times 7+2$, so the day is Monday + 2 = Wednesday. Date: 11 days left in July, 31 in August, 30 in September use 72 days; the remaining 28 days give 28 October.