This feature was exclusively part of a joke version and is not currently planned for addition to regular Minecraft. It is documented here on the wiki due to being officially-released content by Mojang Studios, even if not present in a final version.
Smarter watches were "equipped" by having them placed into the offhand slot. Upon equipping, they would display the current time above the hotbar, in minutes and seconds, with one minute of in-game time being 5/6 of a real-time second, and one in-game hour being 5/6 of a real-time minute or 50 seconds.