About Resource calendars
Every resource in an organization uses a calendar to define working days and hours, as well as track events such as vacation, sick days, and personal days. A Resource calendar uses the Organization calendar as a base calendar. When new resources are added to an Organization, the default Organization calendar is assigned as their base calendar. You can switch the base calendar to any active calendar.
Permission to edit
A resource's supervisor and members of the Resource standard group can edit the working days/times on a resource's personal calendar, as well as add events. The resource can add events only if the Can Edit Calendar attribute is set to Yes; resources are not permitted to change working hours. The resource's supervisor or a member of the Resource standard group can adjust this setting on the resource's Resource Info tab.
Resource calendars and allocations
A resource's capacity hours/week calculation is based on the Resource calendar's working days/hours. Resource calendars do not affect schedules or task dates. However, resources will appear over-allocated/overscheduled if they are allocated/scheduled on non-working days/time from their resource calendar. See Capacity and Calendars for more information.
Where to go from here?
Using Effective Dates for Base Calendars