Recently Google update a new feature into Google+ called "Birthday Reminder". With this update google+ share your birthday or your circle (friends) birthday with you. You will see a notification of your friend’s birthday (from circles) for the day and you can wish them by sending greeting, quotes etc. One more thing that is if you share your birthday with your circles they can also wish you the same. Firstly facebook having this feature now google+ also having the same. Here is the source where you can access the page of this feature : https://plus.google.com/up/birthday
Normally i will use Google+ only few times because it does not have more options than in Facebook and now Google+ also getting few new features and the Birthday remainder is one of them.