It's worth thinking of it the same as strings. Strings can have several encodings, e.g. ASCII, UTF-8 and a hundred others. These are external representation. Yo

It's worth thinking of it the same as strings. Strings can have several encodings, e.g. ASCII, UTF-8 and a hundred others. These are external representation. You don't want to parse the string every time you have to deal with it, so you parse it and store it using (ideally) a single internal representation (e.g. UCS-2, UCS-4). Then, when you need to pass the string to something else, you encode again. Same with dates. Instead of trying to deal with and store all possible representations (format, timezones, etc), you convert all dates to a single representation (hence UTC). When you need to output the date, encode it into whatever format and timezone you need. It's much cleaner this way, because there's less chance you'll mix up representations. So the "for humans" part is more "for developers, which are also humans but like to pretend they aren't and never make mistakes".