Forgetting a special date of yours doesn't mean that the person doesn't care about you at all. Some things need to be understood. I real person who cared about you is when your tough times, He or she is there to lift you, comfort you, and carry also the burden you've carried.
Some time, I also forget a special date of my loved ones. Most often at my busiest moments.
Thank you @mrexperienciado this would help me also to keep on learning about life. It would be a big contribution for me as an individual.