When you create Facebook account, maybe, you enter wrong birthday. So, you need change your birthday if you don't want problem with it. Here's How To Change Your Birthday On Facebook
How to Change Birthday?
Step 1: Go to your profile and click About on your cover photo or you click here
Step 2: Click Contact and Basic Info or you can click here
Step 3: Scroll down and click Edit next to Birth Date or Birth Year (you’ll need to hover over the info you want to edit for the Edit option to appear)
Step 4: Use the dropdown menus to change your birthday
Step 5: Click Save Changes
You can change who can see your birthday by adjusting the audience. There are 2 audience selectors next to your birthday: one for the day and month and one for the year. Friends won’t get a notification about your upcoming birthday if you don’t share the day and month with them.