At the age of 3-4 years, your kiddo has developed a lot. He is developing a clear perception of everything as days go by. He is now moving out of toddlerhood to childhood. He also developed the understanding of time by now.
What you need to know:
Your kiddo has started understanding the concept of time. Make him aware of the value of time. Assign all him work in a specified time frame and gradually set limit for most of his work- playtime, study time, the three meals of the day, etc. Even if he fails, boost his confidence so that next time he is able to keep up his time limit. Inculcating this value will be very beneficial in the long run. You must also practise what you say. Do some of your work like having lunch with him at a specified time, go and come back from the market in the time limit you have set for yourself. Practising this with your child will encourage him to value time. Remember your child is an unshaped clay, he will ultimately take the shape, you want to give him.