How to change the date and time format of clock in panel of Ubuntu

Problem

The Clock on the Panel in Ubuntu displays the time. You can enable it to display the date and day of the week by changing its settings. It displays this information in this format:

Fri Apr 2 02:10 PM

I prefer the following format for date and time display:

2010-04-02 Fri 14:10

The date and time format can be changed to anything that you are comfortable with.

Ubuntu 12.04 and later

Here is how to change the date and time format of the panel clock to your liking:

1. Install the package dconf-tools from the Ubuntu repositories. This installs the dconf-editor which is needed for changing the configuration.

2. Open dconf editor from the Dash or dconf-editor from the shell. In the editor, navigate to com.canonical.indicator.datetime.

3. Change the time-format field to custom.

4. In the custom-time-format field, change the value to the desired format. The format can include both the date and time specifiers. This format uses the same specifiers as that of the C standard library function strftime().

To change to my desired format, I use:

%Y-%m-%d %a %H:%M
2010-04-02 Fri 14:10

The changes should take effect immediately and the date-time should change in the panel.

Tried with: Ubuntu 12.04 and Ubuntu 14.04

Ubuntu 10.04 and older

** Use gconf-editor. Navigate to /apps/panel/applets/clock_screen0/prefs. Change format field to the string custom. Change the custom_format field as described above.