Java has always stored time values as 64-bit longs representing milliseconds since the Unix epoch. This includes System.currentTimeMillis(), as well as what the java.util.Date class uses internally. I'm assuming that the Java 8 date-time API also does this (or something better—either way, I'm certain that it's y2038-compliant).

So, even 32-bit Java is good for another 292 million years or so.