Originally Posted by WHBM

Well, lets get the facts straight then.

Firstly Canada runs along with what the US does in such matters. This is not anything to criticise, it's just practical. Ireland does the same as the UK in such matters for the same reason. But the Canadian government did not choose to do this, they just found it most practical to follow.

Countries that change their clocks are those from about 30 degrees north and south of the Equator. Those inside the tropics do not need to do so. The bulk of the examples given above are in this zone. This is basic physics and how it has always been.

Following the last round of unilateral daylight saving change dates being introduced by governments, in the 1970s, the International Civil Aviation Authority (ICAO), part of the United Nations, drove through an agreement for daylight saving change dates to be the same worldwide. Airline schedules then tagged along so there were major schedule changes twice a year on the same dates. It all worked well, although there were always a few who were different.

This is what the new US approach to time changes has broken. Some of the politicians who led the change did not even know about the international agreement, some didn't care, and some found it a another good opportunity to stick one on the UN.

It's not just a matter of arrivng an hour earlier or later for a few weeks. Connections are broken and at slot-restricted airports there is all the matter of getting new slots (or not) for a short period. Ideally airports where there are restricted slots should give first priority to those carriers from countries who do go along with the internationally-agreed arrangements, over those who do not.