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:

custom

Done!