System.currentTimeMillis(); If I change system time

Question

If I use System.currentTimeMillis() at 00:00 and I get X value.

Then I set the clock back one hour, and after one hour i call System.currentTimeMillis().

Will it return X again, or will it just be X + 3600 * 1000

Answer 1

In a nutshell, whenever you change system time, the value returned by System.currentTimeMillis() will change accordingly.

This is in contrast to System.nanoTime().

Answer 2

It will return X because System.currentTimeMillis() returns the number of milliseconds since the epoch. That means it will be insynch with your clock and count the number of seconds since January 1, 1970 UTC