If the day was truly of importance to you, then it should have been firmly established in your brain patterns. Both the actual birthday of January 15 and the day on which it is observed annually, the third Monday of January.
And what pray tell, had you so occupied that this important day would have escaped from your thoughts? Were you wandering around town distributing face masks with biblical quotes? Serving food at a food kitchen? Bagging and passing out bags of food to those in need? Sucking on plastic Tiddlywinks of assorted colors, attempting to determine if they were of different flavors? Biffing and buffing?