Dear Isamil ,
Firstly , i would like to mention the orcale primavera different types of calenders
1- Global Calendar
2- Project Calendar
3- Resource Calendar
You can assign one calendar for the project as all , but you can also assign different calendars for any activities or wbs .
You can show the calendar column for all the activities and assign each calendar for the activity you want to assign.
You can use the reflection method to make copy of the schedule and use any scenario you want to check and see its impact on your time schedule by assigning different calendars to the same scope for work and activities.