Summarize:

" It's a link in white text on the blue bar in the upper right corner of the browser window. Your browser may automatically sign you into Google+. If this is the case, tap the menu icon. It is a series of three horizontal, white lines located in the upper-left of your screen. " If you have downloaded the Google+ app, it may automatically launch at this point. This method works in the Google+ app, as well. It is a series of three horizontal, white lines located in the upper-left of your screen. " It is the fourth item in the menu. If you have been redirected to the Google+ app, it will be the first menu item. " The link appears in gray text in the upper-right corner of your screen. In the Google+ app, the link will appear in white text. " Depending on how complete your profile is, you may have to scroll several times to locate this menu. It is just below "Places." This a gray pencil to the right of "Gender, birthday, and more." This is a gray circle that contains a white "i" and is located to the right of your birthday. " A blue box will open, asking if you need to edit your birthday, tap on it to be taken to the account page. Located to the right of the birthday info displayed on your screen, the edit icon is a gray pencil. " " Your age is now changed in YouTube.
Tap Your Web Browser App. Go to plus.google.com. Click on "Sign in. Enter your credentials. Tap "Sign In. Tap on the menu icon. Tap "Profile. Tap "About. Scroll to "Gender, birthday, and more. Tap the edit icon. Tap the info icon. Tap "Go to my Account. Tap the edit icon. Update your birthday. Tap "Update. Tap "Confirm.