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Timestamp start = ;
Timestamp end = ;
Duration duration = ;
duration.seconds = end.seconds - start.seconds;
duration.nanos = end.nanos - start.nanos;
if (duration.seconds < 0 && duration.nanos > 0) {
duration.seconds += 1;
duration.nanos -= 1000000000;
} else if (duration.seconds > 0 && duration.nanos < 0) {
duration.seconds -= 1;
duration.nanos += 1000000000;
}