In order to change the working days for your project, access Options from the File menu. In the Options dialog, go to the Schedule tab and check the desired working days from the Default working days group. Another way to change the working days is to select a non-working day from the date-picker pop-up in the Start/Finish column and then, in the Alert message select the Adjust the default working days option from which you have to check the desired working days based on your needs.