Time is an abstract concept, and like money can be difficult for young children to fully understand. These type of concepts have to be revisited often in order for them to be embedded. Learning to tell the time is not the same as understanding time. Being able to read a clock is a memory skill. An essential memory skill, granted, but must be viewed in this context. Just the same as being able to decode a text does not mean a child understands what they are reading, or, memorising times tables is not a measure of understanding multiplication.
Lots of discussions and examples must take place alongside remembering the time phrases we use when ‘telling the time’.