Student learn and practice the formal and informal way to say the time.
The first part is informal and T explains it. For example, It's nine thirty.Then you have some clocks to make your Ss practice
Next, you'll see the formal way. T explains the first part "past/after" . Here you have two ways to practice; first Ss write or say the time but then they have to write the number of the time they see on the ppt. Then explain the second part/side "to".