TIME

A dream featuring the time going by could suggest that you need to be more resourceful or you are facing time constraint in some part of your waking life. 

If you are late in a dream then it can suggest that you need to focus or pay more attention in some part of your waking life, or you are facing a tight deadline.

If you turn up early somewhere in the dream then it can imply that you need to be more patient in some area of your life.

To observe the exact time in the dream could suggest that the numbers you are seeing are of some importance to you.