Working out when an expression formed out of two words has turned into a new word is always something of a black art - yet it happens all the time. Consider cutthroat or bullshit - clearly words these days, but not always. Or more relevantly perhaps, timecard, timepiece or timetable. Whether timezone, timestamp, or filesystem have reached that state yet or not isn't clear - personally, I think they have (and without any wishy washy "a timezone is a technical thing in tzdb and time zone is an area with a common offset from UTC (for some period)". It is also worth noting that the way the transition happens, is for people to simply start writing (and saying, though I think that's definitely already happened for the cases in question) the word pair as a single word and ignoring the "that's not correct" criticism. In my early schooldays (another one) I was taught that the digit '0' was definitely not 'Oh' (that's a letter) and nor was it "zero" (that's American invented nonsense) but a "nought". I can't even imagine the last time I heard anyone use that though (decades ago). The language is continually changing, and we all need to keep up, and not persist in "I was taught..." kre