I went to school with a girl from 3rd through 12th grades who not only had the same birthday as me, but we also shared a first name. I’m older by a few hours.
As for people I’m currently close to, my BFF is 29 days younger than me. She likes to give me shit about the fact that I’ll turn 35 before she does. 
Shirley Ujest and I were born on the same day, same year. I have worked with a guy who was born a couple days earlier or later than me, I can’t recall exactly. It was really close, anyway. One of my closest friends in high school was also born a couple of weeks before me.
One of my classmates shared my birthday. Since he’s a boy and I’m a girl, our parental units deemed it unacceptable to have a shared party, which royally sucked as it pretty much split the class down the middle along gender lines. In anybody else’s party the guests were a mixed group. I’m older than him by 10 hours.
My aunt’s birthday is next day to mine; I’ve met at least 3 other people who go with her and 2 who go the day before me.
Well, my best friend since 9th grade has me beat by 2.5 hours. We have done the joint party thing a few times and it always turns out really well. The best was our 21st which was also shared with our other friend who was born the night before. Shared parties are a lot of fun.
I made friends with one of my neighbours and discovered that he was born on the same day as me - we realised when it came time to invite each other to our birthdays.
Michael Jackson is ten days older than I am.
I have a friend from college who’s one day younger than me. Whether it’s less than 24 hours I’ve never bothered to check. I sometimes joke that she’s the one non-relative who’s birthday I never forget.
The closest was a coworker named Ed. He was born the day after me, by about 7 hours. Of course, that was all I needed to call him kiddo and youngun 
(I had a decent sized crush on Ed)
My cousin was born 12 hours before I was. Our mothers shared a hospital room.
My wife is a little more than 2 months older than me. Otherwise, I don’t think I even know anyone’s birthdays.
Hah, had to take a trip to my past posts to figure out why the heck you would know my birthday. 
I turned 30 that day.
I was born on the same day as baseball Hall of Famer Rod Carew, but I don’t know his time.
I share a birthday with Australian rules footballer Mark “Jacko” Jackson, known in the USA for some Energizer battery commercials that aired about 25 years ago. Because of time zone differences, he’s probably more than 24 hours my senior, as I was born at around 10 p.m. in Ohio. I share a birth month with quite a list – actress Rebecca De Mornay (August 29), actor/reality show personality Danny Bonaduce, and basketball star Earvin “Magic” Johnson, among others.
One of my best friends is about 10 hours younger than I, though her birthday is the next day.
My best friend in elementary school shared a birthday with me – but he was a year older (he’d stayed back a grade).
My sister-in-law is 2 days younger than me.
And the celebrity who’s nearest in age to me are John Edwards, Tim Allen, and Benazir Bhutto, all a few weeks older.
I have a coworker who is five months older and another who is four months younger. Beyond that, I don’t know anyone personally who is closer to me in age, although I wouldn’t be surprised to learn there are Dopers here who are in that range.
In fact, I think I’ll start a thread about it.
I’m a day younger than Traci Lords.
I’ve met someone born within 15 minutes of me. She went to the same college as me, had the same major as me, played the same instrument as me (so we sat next to each other in band/orchestra) and we got along horribly.
Since I’ve never really mentioned it on here, and haven’t read any of the birthday threads…I’m curious if anyone reading this shares the same birthday as me. May 13, 1980, 8:31AM EDT.
Through part of middle school, I went to school with a boy who was born two days after me in the same hospital. We were the only two babies in the nursery. Then I met someone in college born 4 days after me.