You may not want to have Monday as the first day of the week, but perhaps prefer to start your week on a Tuesday.
To do this click "Settings" then "Users" then click the name of the user for whom you would like to make this change, scroll down until you see "Calendar settings" and the section which is called "First day" as circled below:
If you click the arrow on the right hand side of the text box:
A drop down menu will appear which will allow you to select the day of the week you would like to use:
Once you've picked the day of the week you would like to start your calendar view from, in this example, I have selected Tuesday:
Ensure you click "Save" in the top left hand corner:
This change will then be reflected in your appointment calendar, the week now starts on Tuesday rather than Monday: