The notion of time is acquired by the child with some slowness. At the beginning he has a very specific concept of space: his house, his street; He has no idea where he lives. But that notion develops more quickly than that of time, because it has more sensitive references.
Time is an abstract concept: it cannot be seen or touched. That is why the passage of time and the sequence of it are so difficult for children’s minds to understand. They live in the present, they do not consider what will happen in the future, however close it may be, nor are they aware of having starred in a past.
The words now, today, yesterday and tomorrow can point in their use, each time a different sector of real time. The child is oriented in time based on habits or daily routines such as, for example, going to school or sitting down to dinner.
Remember that your child learns everything through play, so to teach him these notions you should also use calendars and children‘s clocks, stories in which the moon and the sun appear, to differentiate day from night, etc …