public DateTime withMillis(long newMillis)
The returned object will be either be a new instance or this. Only the millis will change, the chronology and time zone are kept.
newMillis - the new millis, from 1970-01-01T00:00:00Zhttp://www.joda.org/joda-time/
原文：http://www.cnblogs.com/softidea/p/5905573.html