According to this article, since Windows Phone 8.1 you don't need a SIM-card in your phone to have it automatically adjust the built-in clock, since 8.1 supports NTP for this purpose, not just using the GSM network's time, which previous versions were limited to.
This does not work for me, and I seem to have that problem in common with a lot of the people commenting on that article. I do have an option under Date & Time "Set automatically" which is enabled (and I have switched that option back and forth several times, to no avail).
Everything else network-related works as expected, with one exception: software updates fail because my clock is out of sync (updating from 8.0 to 8.1 worked with the same clock settings but after that it is a dead end). Any workaround?
What am I and a lot of the people commenting doing wrong?