A resource calendar is a calendar that identifies the working days and shifts on which each specific resource is available. Information on which resources (such as human resources, equipment, and material) are potentially available during a planned activity period, is used for estimating resource utilization. Resource calendars specify when and how long identified project resources will be available during the project. This information may be at the activity or project level. This knowledge includes consideration of attributes such as resource experience and/or skill level, as well as various geographical locations from which the resources originate and when they may be available.