My sister made this cute magnet board to keep track of birthdays and anniversaries. She used vinyl to separate the magnet sheet into months and then printed out a piece of paper for each member of the family with their name and date of birth on it. She also included anniversaries. Then she backed the paper with magnet strip tape. There are a ton of possibilities for how you do the magnets. Check out this, this, and this for more great ideas on magnets.
I love this idea because it is a great way to make room for more birthdays and anniversaries as new additions join the family.