Thank goodness birthdays only come around once per year.
In my opinion, wishing someone a happy birthday is not a sign of friendship, approval, or even a sincere wish of happiness. A “happy birthday” is a general acknowledgement that it’s 2015, and one or more of my social media sites informed me that you were born X amount of years ago today. I am simply letting you know I am aware of said fact, maybe with a few emojis thrown in for good measure. It may not be heartfelt, but there’s no need to make it awkward. If you’re my friend, you’ll know, and won’t need to judge it on the basis of whether or not I wished you a happy birthday or not.