I have a two year old and a 4 year old that are in half day preschool. Responsibilities would include playing with them for a bit after school and then putting them down for a nap. On Fridays they do not have school so it would be a full day (9:30-2:30).
Unfortunately my schedule changes every week so we do need some flexibility. We typically need help 1-2 days a week. Mondays and Wednesdays will be from 12:30-2:30. Fridays will be 9:30-2:30. I only work 3 days a week, but the days are different each week.