Research shows that children do not truly understand the concept of time until the first or second grade. Even though your son might be able to memorize the days of the week, he does not have a true understanding of what a day is. With this in mind, focus on introducing him to concepts such as before and after, and talk to him about what he did yesterday and what he wants to do tomorrow. Doing this is a great way to help him understand the difference between past and future. If you would like to introduce your son to a calendar, you can purchase one (my favorite is One Step Ahead’s “My First Daily Planner”) or make one with him. Have your son change the day of the week and the date each day, and use the calendar to mark special events so that he begins to understand the purpose of calendars.