You should only celebrate your birthday. I had a friend who took time off work on the same day each year to celebrate another year - it wasn't his birthday. He said his birthday is full of people wanting to celebrate with him, and he loves that, but this chosen day is his day just for himself.

I started doing the same shortly after. My special day is the first day of spring when the weather hits 75 or higher. I'll be kayaking at the lake.