Don’t forget that Date constructor happily accepts negative values.
Date date = new Date(Long.MIN_VALUE);
returns
Sun Dec 02 22:47:04 BDT 292269055
I guess that’s about the time of Big Bang dinosaurs 🙂
EDIT
As martin clayton answered, you can use the Calendar class to check the era. This will output 0 which stands for BCE:
Calendar calendar = Calendar.getInstance();
calendar.setTime(new Date(Long.MIN_VALUE));
System.out.println(calendar.get(Calendar.ERA));