I was on fb for a couple of months like 7 or 8 yrs ago. It was new and I was naive about how it worked so I treated it like signing up for anything else online (because I'm cautious) so I gave a fake bday of Jan 1. I signed up before new years and first a few people I knew wanted to 'friend me', the next day many more, the next day many, many more. Come New Years Day everyone is wishing me "Happy Bday!" Only 1 out of the 100 or so friends actually said "Why do you have your bday set as 1/1?" He was the only real friend I had on fb and new my real bday. Got rid of my fb account cuz I saw it as silly and have never been back.
p.s. I also don't own a cell phone and it does not bother me. [Most common response is "Do you know what year it is?" [Yes 2017 almost 18.]
p.p.s. Realize I'm posting an anti-social media comment on what is essentially a social media site on which I have an account. Yes - I have an account and yes I make occasional comments but I don't care about karma and my friends and family don't know my user name.