Three main differences between prom and homecoming: 1.The date. Proms are generally held from March to June, while homecoming usually occurs in September or October, which is often viewed as a kind of welcome-back activity. 2.Participant. Prom is for seniors and sometimes juniors,while homecoming is open to all students. 3.Dress code. Prom is typically very formal, while homecoming is usually much more casual.