To assign a factory calendar, you can use the network header. The network header is a structural element of a network that contains general data and settings for a network, such as its order type, number range, scheduling parameters, and so on. The network header also contains the factory calendar field, which allows you to assign a factory calendar to a network. A factory calendar is a parameter that defines the working days and holidays for a plant or a location. A factory calendar is used to determine the dates and durations of activities and networks based on their workdays and non-workdays. Reference:https://help.sap.com/doc/0f069b2e08b748f1b480d4c8b46c3c49/100/en-US/6a7a9f0a6e421014e10000000a174cb4.html