It's not because he gives a wonderfully description of the problem and solution that makes you fully understand what happened. What makes it incredible It's that he solved it so comprehensively in 15 minutes from the time the poster asked the question. Most high calibre devs would be still wrapping their head around the problem after 15 minutes.
Most high calibre devs haven't stumbled into doing a lot of date/time work. That wasn't some clever decision on my part - it was working on the calendar part of Google Mobile Sync. Date and time is a rabbit hole that I just went deep on. A bit of luck rather than spectacular wide knowledge, I'm afraid.
I love that question and answer too, although I doubt that it's genuinely helped many people. Time zone and calendar stuff has a lot of amusing trivia. My favourite involves the 30th of February, which only occurred in 1712, and only in Sweden.
Having said that, politicians changing DST rules with a few weeks notice (like Turkey last autumn) are nuts. The impact of such decisions is huge and worldwide (emergency patches etc.)
Man, now I know there's something worse than being born on the 29th of February and having 1/4th the birthdays. :)
This is good evidence that humility is correlated with mastery.