One way is to get in the habit of looking at digital clocks in real life, looking away, and looking back.
When you do this in a dream the time will always be different the second time you look at a clock. And, it might be nonsensical such as 39:73.
In order to do this in the dream, you must always do this whenever you see a clock while away. It's not as difficult as it may seem. It worked for me after just a few days a clock watching.
