ubuntu 13.10 不显示时间 解决方案

Already solved here and here.

From the terminal:

sudo apt-get install indicator-datetime
sudo dpkg-reconfigure --frontend noninteractive tzdata
sudo killall unity-panel-service

Then logout & login from the graphic session.

If the clock is still hidden/grayed out:

Time&Date panel --> Clock --> Show a clock in the menu bar

If it still doesn't work report a bug on Launchpad.

*edited to solve a bigger slice of problems.