I guess kudos for doing a deep dive into this, but was it necessary?
Aren't all of these types of things (unhappiest day of the year, best day to be born on, age that we're happiest etc) clearly pseudo-scientific/scientistic babble - and brands can then just use them to sell the Scandi (or whatever) lifestyle. Nobody who believes this is going to be swayed by your anaylsis. :)
The survey being used was created by a Princeton University psychology professor. It may or may not be useful but there's nothing obviously pseudo-scientific about it. I do not think the linked article writer is making that claim.
Yes, it's necessary, and getting more so all the time: lately I've been seeing more and more commentary trying to tie happiness measurements to some political stance: "conservatives are happier than liberals", "women are happier after divorce", etc. And increasingly it's not coming just from random commenters, but from people with real power.
In such an environment it's vital to know if the methodology for measuring happiness is good or bunk.
How much of the article did you read? The main substance of it is not that the UN rankings are flawed, but how the rankings change based on the broader analysis by Blanchflower and Bryson. That result can't so easily be read off from our cynical preconceptions
Should outlets like the NYT be reporting uncritically on pseudoscience? As long as they are I think this kind of work is extremely valuable.