Calendars are created to designate non-working days for a area, division, or company. After setting up a calendar, it is necessary to go and apply that calendar to the company, area, or division as needed. The Scheduling module will look to see if there is a calendar assigned (i.e., a calendar is selected) and if so, it will use that calendar when calculating scheduling activities. The calendar lookup goes in the following order:
At the area level (Setup > Areas > Edit or New Area > Scheduling tab).
At the division level (Setup > Divisions > Calendar tab)
At the company level (Setup > Company > Calendar tab)
Rather than setting up "holidays," a non-working day is defined in a calendar by creating an entry on that date. Setting up non-working days enables the software to take those days into consideration when calculating the schedules in the Scheduling module. The schedule baseline and projected dates will calculate excluding non-working days. The work week and non-working day calendars work in tandem, (the software looks to the work week first, then looks at the calendar assigned; if the day is a non-working day in the calendar, the software moves to the very next day when computing).
First create as many calendars needed, then go into the respective places to assign the calendar. Once a calendar is assigned, it can have changes made to it and update scheduling activities only if that
From the Setup menu, select Workday Calendars.
Or, click on the Workday Calendars icon on the Setup toolbar.
From the Workday Calendars menu, select New Calendar.
Or, click on the New Calendar icon.
Type a name for the calendar. For example, "Division 1 2007 calendar."
Click OK.
To designate a non-working day, navigate to the desired month in the calendar and click on that date.
To go to the current date at any point, select Go To Today from the Workday Calendars menu, or click on the Go To Today icon.
Select New Entry from the Workday Calendars drop-down menu, or click on the 
New Entry icon, or right-click on the date and select New Entry.
Type a description for the non-working day.
Click OK.
Repeat steps 5-8 for each non-working day in the calendar for as many years in advance as desired.
Click on Save.
When finished, click Close to exit the screen.
Defining the Company Work Week and Calendar
Defining the Division Work Week