A common pitfall I see developers stumble on is underestimating how often timezones, DST rules, etc change. In most of our daily lives this is something that happens very rarely, right? However, if you go look at the change logs for DST rules, timezones, etc, you'll see that as a ballpark figure there's at least one change a year, and on many years more. Once a year is way too often to not account for this data changing and the recommendations given in this article are solid.