As someone who sees MS Word forms regularly force Canadians to use Month/Day/Year formats which were never native to Canada and don’t meet the ISO standard either, I am inferring the impetus transition.

But truly, I old enough to recall many standards being harmonized in the early 90s in the wake of the North American free trade agreement.

Whether or not a digital archive document demonstrates that Canada Post intentionally harmonized to match the US is TBC.

But it is a verifiable fact that the two-letter standard for provinces and territories has not been commonly established in all federal regulations or data standards or in provincial and territorial data systems standards.

That is to say, it has not been formally adopted as by Canada or as the ‘Canadian data standard.’