I experience this in the early hours of the morning,about once every 3 or 4 months. Strangely enough,it happened this morning. I had woken up,but was not fully awake,when I thought I heard a sharp rapping on the front door. It was only 7 am. My foolproof way to check is to look at my cat,who always sleeps at the foot of my bed. If she looks agitated,and is looking towards the bedroom door with her ears pricked forward,I know that I probably DID hear someone knocking. If she hasn't stirred, (like this morning) I know it's nothing to worry about.
How do you acknowledge Easter.