How about System.currentTimeMillis()?
From the JavaDoc:
Returns: the difference, measured in milliseconds, between the current time and midnight, January 1, 1970 UTC
Java 8 introduces the java.time framework, particularly the Instant class which “…models a … point on the time-line…“:
long now = Instant.now().toEpochMilli();
Returns: the number of milliseconds since the epoch of 1970-01-01T00:00:00Z — i.e. pretty much the same as above 🙂