Kepler - Color fields | SLA & Custom actions app gives you the possibility to add one or more working calendars (I. Configure a working calendar)

The configuration of the SLA needs to be assigned to a working calendar

Click on the tab 'Planning', to assign a calendar of the working day to the SLA 

Assign a working calendar

1. Choose a calendar from the list of the calendars that are created in part (I. Configure a working calendar)
2. Save the assignment by clicking on 'Done'.  Or, click on 'Cancel', to cancel the assignment.

To configure a Scheduler, click on the tab 'Scheduler'