Unfortunately, it is kind of on purpose. The .desktop file has OnlyShowIn=Unity; otherwise there will be multiple Time & Date options in gnome-control-center. There is a workaround though:
XDG_CURRENT_DESKTOP=Unity gnome-control-center indicator-datetime;
I suppose indicator-datetime could force that environment when it execs gnome-control-center, but otherwise I'm not really sure how to fix this issue.
Unfortunately, it is kind of on purpose. The .desktop file has OnlyShowIn=Unity; otherwise there will be multiple Time & Date options in gnome-control- center. There is a workaround though:
XDG_CURRENT_ DESKTOP= Unity gnome-control- center indicator-datetime;
I suppose indicator-datetime could force that environment when it execs gnome-control- center, but otherwise I'm not really sure how to fix this issue.