Debatable - the concept of leap years was invented before 0 AD/CE but I'm not aware of any reason to believe that particular year (which certainly wasn't called 0 AD at the time, it was possibly the Roman year 753) was considered to be one.
Interesting that there seem to be a large number of scholars who would accept either 4 AD or 8 AD was the first AD leap year. But less clear what such a year would have been called by Romans at the time. I'm assuming it wasn't common to include full dates (including the year #) on written documents at the time, otherwise surely we'd know pretty much exactly.
I gather AD-based year numbering wasn't actually introduced until ~525 AD (but before that a number of systems had been in use).
0 is a year if we say it is, which astronomers have for hundreds of years (because its extremely mathematically convenient), and which ISO-8601 does.
Year 0 is what historians like to call 1 BC, but historians are also just making that up. Nobody numbered years from Anno Domini anywhere near year 0.
I'm sure it's clear to everybody here why year 0, -1, and -2 are significantly better arbitrary, ahistorical names for the three years preceding year 1.
