/**
* @param instant instant from 1970-01-01T00:00:00 local time
* @return instant from 1970-01-01T00:00:00Z
*/
private long localToUTC(long instant) {
DateTimeZone zone = getZone();
int offset = zone.getOffsetFromLocal(instant);
instant -= offset;
if (offset != zone.getOffset(instant)) {
throw new IllegalArgumentException(
"Illegal instant due to time zone offset transition: "
+ DateTimeFormat.forPattern("yyyy-MM-dd'T'HH:mm:ss.SSS").print(new Instant(instant)));
}
return instant;
}
