The CALID statement specifies the name of a SAS variable that is used in the Activity, Holiday, and Calendar data sets to identify the calendar to which each observation refers. This variable can be either numeric or character depending on whether the different calendars are identified by unique numbers or names. If this variable is not found in any of the three data sets, PROC CPM looks for a default variable named _CAL_ in each data set (a warning message is then printed to the log). In the Activity data set, this variable specifies the calendar used by the activity in the given observation. Each calendar in the project is defined using the Workday, Calendar, and Holiday data sets. Each observation of the Calendar data set defines a standard work week through the shift patterns as defined by the Workday data set and a standard day length; these values are associated with the calendar identified by the value of the calendar variable in that observation. Likewise, each observation of the Holiday data set defines a holiday for the calendar identified by the value of the calendar variable.

If there is no calendar variable in the Activity data set, all activities are assumed to follow the default calendar. If there is no calendar variable in the Holiday data set, all of the holidays specified are assumed to occur in all the calendars. If there is no calendar variable in the Calendar data set, the first observation is assumed to define the default work week (which is also followed by any calendar that might be defined in the Holiday data set), and all subsequent observations are ignored. See the section Multiple Calendars for further information.