Add or change your birthday on Google+
When you sign up for a Google Account, you may be asked to add your birthday. Knowing your birthday helps us use age-appropriate settings for your account. For example, minors may see a warning when we think they’ve found a site they may not want to see.
Add or edit your birthday
Important: Changing your birthday in Google+ will change it on all Google products.
Android / Mobile Web / iPhone/iPadYou can’t update your birthday on mobile devices just yet. Please use a computer to add or change your birthday.
- Open Google+ > click the drop-down menu in the top left corner
> Profile
- Click About below your cover photo > scroll to the “Basic Information” box.
- Click Edit in the lower left corner.
- Type your birthday > click Save in the lower right corner.
> Profile 
Hide or show your birthday
You don’t need to show your birthday to others unless you want to. By default, the people in your Google+ circles can see the day you were born, but not the year. If you’d like to keep your birthday private, you can use your settings to choose who sees that information on your Google+ profile.
Android / Mobile Web / iPhone/iPadYou can’t update your birthday on mobile devices just yet. Please use a desktop computer to add or change your birthday.
- Open Google+ > click the drop-down menu in the top left corner
.
- Click About below your cover photo and scroll to your card.
- Click Edit in the lower left corner of the card.
- When you edit your information, use the drop-down menu on the right to decide who sees your information.
- If you make changes, click Save in the bottom right corner.