To add a holiday to the Project Calendar click on Project – Change Working Time. In the For calendar list, click the calendar you want to change. For holidays, use the current project calendar. It has the words (Project Calendar) after its name. For vacation days, use the person’s resource calendar. It has the same name as that person. On the Exceptions tab, add a name, start date, and finish date for each holiday or vacation day. Project reschedules tasks around the new nonworking time.​