Yes, here are the steps:
Open your project. Click the arrow next to the Calendar language and choose Language Editor from the drop-down list.
Choose your language, in our case, it's English, and switch to the Weekday Names tab. Now type in the desired names for one of the shorter variants. We replaced every day name with one letter. Click Save to apply the changes.
Now go to the Month Style and make sure that this variant is chosen for both Weekday Names and Weekend Names:
Here is what you should get in the end: