Merlin provides a user friendly interface to modifying the project calendar. In previous versions, the project calendar was found in the project settings.
Project calendar is now an inspector tab. To access it, select the project row (row #0) in the outline area of the Activities View and click on the 'Working Time' tab in the inspector.
You can change the project calendar to accommodate for project wide events such as national holidays.
If you wish to re-use your project calendar in other projects, you can export/import calendars by clicking on the gear icon
Note: If you already have the exceptions on an iCal calendar, there is no need for you to enter them manually in Merlin. You can simply use the gear icon and import the iCal file into the selected Merlin calendar.