...
WBS Gantt-Chart ⇒ Choose Gantt Configure.
Click Edit of Calendar.
...
Edit holiday calendar settings:
Choose using shared calendar or Gantt individual settings calendar
Check the non-working days in Regular holiday
Choose Week Number style (US or ISO-8061)
For individual holidays
...
Enter them to the Holiday list
Or import the holidays from public calendar.
Click Update.
You’ve now completed the basic configuration. Next, let’s try managing a project.
...