MS Project Calendars

• There are (3) Calendars in MS Project
• They can seem to fight one another until you learn how they work.

Calendars determine whether or not a task is progressing during a given period of time.

Let's say you have an 8:00am to 5:00pm working time in your calendar. At 5:01pm, MS Project assumes that no further progress will be made until 8:00am the next day.

But if you decide to add a night shift from 8:00pm to 5:00am, the work will progress overnight. The project or task will finish sooner.

The 3 Calendars

There are 3 calendars in MS Project:

• The overall Project Calendar
• Resource Calendars
• Task Calendars

The Project Calendar

If you don't assign any resources, MS Project will use the Project Calendar exclusively to determine whether or not work is progressing on your tasks.

The Project Calendar can be found under the Project tab, under the button Project Information.

After clicking on Project Information, you will get a dialog box that allows you to select the overall project calendar that will be used by tasks on the project.

Note: Right out of the box, MS Project includes Standard, 24 Hours and Night Shift as work schedules that you can select as calendars. You can modify or make your own, which is covered in another article..

To reiterate, as long as you don't assign resources, all of your tasks will follow the Project Calendar.

Resource Calendars

Each resource on a project can have it's own calendar. You can find the calendar for each resource under the view Resource Sheet.

In the image below, Bob has the Standard calendar, which is 8-hrs per day, and A-1 Piping has the 24 Hours calendar, which means it is available around the clock.

For any new resources, MS Project assign the same calendar Resource Calendar as the current Project Calendar.

• If you current Project Calendar is Standard, any new resources will automatically get the Standard calendar.
• If you then change your Project Calendar to 24 Hours, any new resources after the change will get assigned the calendar 24 Hours.
• Note: You can change Resource Calendars to anything you want, using the Resource Sheet View.

Resource Calendars take priority over the Project Calendar.

Let's say you have an aggressive project schedule, with 7 days per week, 12-hrs per day, for a Project Schedule.

However, there is one task that only Bob Smith can do. And Bob can only work 4 days per week, and 8-hr days. As soon as you assign Bob Smith as a resource for a task, the task will stretch out.

Let's try it. The image below is for a project calendar with a 12-hr working days, from 8:00am to 8:00pm.

So the three 4-hr tasks fit exactly within one 12-hr working day.

Now let's assign Bob, who works an 8-hr day. Notice how the tasks have to stretch to the next day.

If you don't understand what it going on, it can be very frustrating. But what MS Project is doing makes perfect sense. Regardless of the Project Calendar, if a specific resource is not available during a certain period of time, the task simply will not progress.

If Bob takes one month off to celebrate Festivus every year, you can put that in his resource calendar as well.

Resource Calendars may have a place for certain types of schedule, but I believe task calendars provide the most amount of flexibility and transparency for industrial type schedules.

Task Calendars

• Task Calendars are great when you have a variety of work schedules on a project

If your schedule is industrial in nature, you might need a lot of flexibility. I have done a lot of shutdown planning, and you can get a large variety of schedules.

You might have the same contractor (resource) working day shift only on one part of the work, but around the clock on the critical path section of the work. This makes it hard to use the Resource Calendar

Task Calendars provide the ultimate in flexibility.
The article Task Calendars covers how to use them.

References