On Ubuntu Unity 18.04, The default datetime format is quite weird.
If you displayed week, It would show up "三" instead of "星期三".
So you have to change this.
Install dconf Editor
sudo apt install dconf-editor
launch dconf-editor and go to:
com -> canonical -> indicator -> datetime
open "custom time format" and change it to:
%A %l:%M %p
Open "com -> canonical -> indicator -> datetime -> timeformat" and set it to: