7th October 2016, 10:40
Exactly as leszek stated, you have to set the regional settings to the one that has Monday as the 1st day. What I do is I go to the System Settings->Account Settings->Formats, there I set the Region to American (since I want to have the environment in English) and then check the Detailed Settings checkbox, and in it I set all of the settings to my country. After logout/login you will see the calendar in format of your country.