Convert iOS timestamp to Java Date time (milliseconds)

iOStoEpochTime.java

import java.util.Calendar;

long IOSOFFSET=-1;

// parameter "t" is a iOS timestamp, stored as seconds since Jan 1, 2001.
long iOStoEpochTime(long t) {
  
  // calculate IOSOFFSET if necessary
  if (IOSOFFSET<0) {
    // Objective-C timestamps are in seconds since Jan 1, 2001, while 
    // Java timestamps are in milliseconds since Jan 1, 1970. Hence we
    // need to calculate a timestamp IOSOFFSET (in msec) between those two
    // dates.
    Calendar cal=Calendar.getInstance();
    cal.clear();
    
    // get start value
    cal.set(1970, Calendar.JANUARY, 1);  
    long tmp=cal.getTimeInMillis();

    // get final value
    cal.set(2001, Calendar.JANUARY, 1);
    
    // offset is the difference
    IOSOFFSET=cal.getTimeInMillis()-tmp;
  }

  // t is in seconds, so multiply x1000 to get millis,
  // then add IOSOFFSET to get. "1000l" means "1000 as
  // a long"
  return t*1000l+IOSOFFSET;
}