A fictional year, generally thought to happen after the year 2000. Comparable to the month of Octember or the time 13 o'clock, in that it doesn't exist in 'real time'. The term '20XY' is often used to refer to an undetermined year in the future. A certain train in Hong Kong can take you here. A train to lost memories. A train to lost memories... lost memories of the future.
'Real Time' as it Relates to '20XY'
Real time, in this context, is the time we as people actually experience. The year 20XY, among other things, exists outside of real time. As such, we don't experience it in our normal conscious states. See the article on Real time for a more in-depth discussion of the theory.