At this point, your child will begin to comprehend the concept of time in terms of days clearly. They can express and understand today, tomorrow and yesterday with words properly.
What you need to know
Start slowly and teach him to make a paper clock with movable hands and regularly practice with him. At first, explain to him how the minute hand and the hour hand works. Put the hour hand at various positions and explain to him what the clock reads.
You might consider buying him a watch to wear and consider replacing the digital clock in his room with an analog one. Keep asking him the time for school bus, breakfast, TV show, park time, dinner time or bedtime. Ask him to check the time by himself. Tell him to make a list of important times of the day. Once he understands the basics, add more complicated time concepts. Follow these simple method and very soon you would notice that he is comfortable with reading the time.