riddle - Who am I, and when will I appear? the second

(with apologies to @Rand al'Thor, whose latest puzzle inspired me to post this one, my first here—and whose text I blatantly stole lovingly adapted in homage.)

I came regularly once a year, from '92 to '95,
Skipped 1996 entirely,
Returned in 1997, and took a break after 1998.
I made a few appearances between '05 and '13,
But in '15 I was back like clockwork.
This year I haven't appeared at all!

Who am I? And when will I next appear?

Answer

This is from a comment by FumbleFingers, who should feel free to make a separate answer and get full credit.

           ^{(source Wikipedia)}

Who am I?

A leap second

          Last seen:

^{(from Wikipedia)}

And when will I next appear?

Saturday

December 31, 2016, at 23:59:60 UTC