How to make date show day/month/year in numbers instead of letters and words?

At the moment, this is how the date and clock looks like in Ubuntu's top bar:

In Estonian, "R" stands for "Reede" or "Friday", and "Juuli" means "July".

How can I make the date show day/month/year in numbers instead of letters and words?

Your question is similar to this one (not sure if it should be considered a duplicate), so I'm copying my answer from there, modifying the clock format to the one you want.

There are several extensions in the GNOME Shell Extensions website, but most of them are not actively supported anymore. I'm suggesting you to use the Panel Date Format extension, which works fine on Ubuntu 20.04 and is still maintained.

• Read this question about how to install GNOME Shell extensions: How do I install and manage GNOME Shell extensions?

To customize your clock after installing the extension, follow these steps:

1. Open Extensions, find the Panel Date Format extension in the list and click the gear icon next to it.

2. You will be presented with this Preferences menu (image from the extension's GitHub repository):

   

3. In the Format textbox enter the following to get the time format you want:

   %d/%m/%Y %H:%M
   

   You can find more info about the date time format syntax here (link also mentioned in the extension's preferences).

4. Restart GNOME Shell to ensure that the setting is applied by pressing Alt+F2, entering r and pressing Enter.

Your panel's clock should now have the appearance you want!