How many times have you got a millisecond long timestamp and had to compare it to a duration e.g. 1000 * 60 * 60 * 24 * … ? I stumbled upon this more readable and less error prone way of representing, say, 5 hours, by using the java.util.concurrent.TimeUnit.
private static final long FIVE_HOURS = TimeUnit.MILLISECONDS.convert(5, TimeUnit.HOURS);
...
if (timestamp < System.currentTimeMillis() - FIVE_HOURS) {
// do something.
}
The above will check if a timestamp is overdue for more than five hours. The variable twoDays will have the value 172800000. TimeUnit supports from nanoseconds, micro-, milli-, all the way up to days.
However, if the date/locale is important to you (e.g. daylight savings) then you should use the Calendar API/JodaTime rather than this "duration"-based TimeUnit.