User: set an alarm in eight hours.
It's 10PM right now. At what time should the alarm be set? 6AM? Woops, tomorrow is the switch to DST! What now?
User: remind me to brush my teeth on November 21st at 8AM.
Okay, will do! Wait, you took a plane on November 2nd and are now on the other side of the world? Should I remind you at 8AM or 5PM?
User: please note my doctor's appointment in two weeks at 10AM.
Sure thing bub! Wait, but you live in Morocco in 2019? And the government just announced that reverse DST will be in effect for the month of Ramadan, which begins next week?! WTF do I do now?
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tl;dr It's not just an issue of storage. Managing time is hard. There are requirements that we, as humans, will intuitively find the right interpretation for, that computers will absolutely break their teeth on.