Microsoft Project schedules tasks based on the project calendar, but it is possible to define a unique task calendar specific to a situation. These are called task calendars.
Typically, most work on a project is performed using the same schedule. Perhaps, an 8-hour per day five day week schedule or a 10-hour per day four day week schedule. It makes sense to define a project calendar that accounts for this common work time schedule and any respective shared holidays.
There are times though when a particular task requires its own unique calendar. In these situations you want to define a calendar that you can assign directly to a task; a task calendar that holds true only during an assigned task effort.
This article discusses the purpose and value of task calendars using Microsoft Project.
There are three types of calendars available for definition in Microsoft Project: project calendars, task calendars, and resource calendars. Again, project calendars specify task start and finish times based on a shared hours per day schedule and holidays. Resource calendars help define availability of specific personnel. For example you can create a unique calendar for a worker that is on vacation the last two weeks of August.
When this calendar is assigned to the respective resource Microsoft Project will raise a warning flag, if you schedule this resource to work on any task during the last two weeks of August. So unique calendars can be associated with specific resources.
It is also possible to define a unique calendar and assign it to one or more individual tasks. The following are situations when a task calendar comes in handy:
Modeling Concrete Cure time: concrete cures 24-7, so you want to model your concrete as curing seven days a week, which includes the weekend. So create a concrete cure 7-day work week calendar and assign it to all your concrete cure tasks.
Winter Weather: If you cannot install asphalt during the winter months in your location you will want to assign the asphalt paving tasks a unique calendar that has this period of winter blocked out as non-work time.
Equipment Availability: If your lab equipment has limited availability, create a unique lab work day calendar defining availability days as work days.
Office Moving: Limit company downtime by moving office and lab equipment on weekends. Create a moving calendar for these tasks where only weekends are work days.
Summary
In Microsoft Project, when a project calendar is not a suitable fit for certain schedule activities, create a task calendar. This can help to uniquely define this schedule situation. You may want to note the order of precedence for the three calendar types. Task calendars override resource calendars, which override project calendars. Task calendars therefore take precedence. But conflicts between task calendars and resource calendars are a known possibility.