> Every system can handle a leap-hour, they happen twice a year in many countries, courtesy of DST. Any DST aware system I've checked handles this as a timezon

> Every system can handle a leap-hour, they happen twice a year in many countries, courtesy of DST. Any DST aware system I've checked handles this as a timezone change rather than changing the underlying time, expressed in UTC. Even for locations where DST's onset removes an hour rather than adding one.