Project Calendar Vs Resource Calendar



By Fahad Usmani, PMP®, PMI-RMP®,

PM Study Circle contributing

In project management, we have two calendars to help organize work and resources. These two calendars are:

  1. Project calendar
  2. Resource calendar

These calendars are developed in the planning phase and are updated throughout the project. However, modifications to these calendars are not as frequent as for some other documents like the stakeholder register, risk register, lessons learned register, etc.

These calendars are usually a graphical chart, and a quick look at them will provide you with a great deal of useful information.

Let’s discuss these calendars in detail and how they are useful in project management.

Project Calendars

project calendar

These calendars help you identify working days and shifts available so that you can plan your activities. Project calendars are useful for developing the schedule.

In a project schedule, you can use more than one project calendar for different work periods. You can update these project calendars if and when required, for example, when the government announces public holidays or a holiday is canceled.

Project calendars are vital in emergencies. They show you non-working days, and you can plan urgent tasks on these days or shifts to tackle a crisis. These calendars also help you plan overtime and compress the schedule.

Let us summarize some key points about a project calendar:

  • It shows the days, shifts, and times when you can work.
  • It helps compress the schedule.
  • A schedule can have more than one project calendar.

In the PMBOK Guide, the project calendar is an output of the schedule development process and is one of the organization process’s assets.

Resource Calendars

resource calendar

Resource calendars help you identify when and how long a specific resource is available for your project.

If your project is a part of a portfolio or program that has multiple shared resources, you can quickly identify when a shared resource is available for you, and then you can plan its usage accordingly.

This information is required for schedule development.

Resource calendars can have some attributes such as experience, educational qualifications, and equipment type.

Let’s summarize the key points about resource calendars:

  • Resource calendars show the availability of resources.
  • They are very useful when resources are shared with other projects.
  • The resource calendar includes human resources, equipment, consumables, etc.

In the PMBOK Guide, resource calendars are an input of the estimate activity resources process and are a part of the staff management plan.

Project Calendars vs Resource Calendars

Because of their similarity in name, many professionals think these two calendars serve the same purpose and are interchangeable. This is not true. Both calendars are different and serve different purposes so you cannot compare them with each other.

Project calendars show when you can work and when you cannot, while resource calendars show resource availability for your project.

The information available in a resource calendar is more dynamic than in project calendars, and changes to a resource calendar are frequent. The project calendar has mostly fixed information like weekends and holidays, so changes are less frequent.

You can see that these two calendars complement each other, they do not compete.

A Real-World Example of the Project Calendar and Resource Calendar

Let us say you want to paint your house next month and it has six rooms.

You plan to finish this project in 14 days (two weeks), and you are going to develop a project calendar to help you.

Since you attend college five days a week from 8:00 am to 2:00 pm, you mark this duration as a non-working shift and plan to work from 4:00 pm to 7:00 pm on weekdays.

Saturday and Sunday are weekends, so you are free. Therefore you plan to work on weekends from 9:00 to 4:00 pm.

During the second week, you are going to a wedding on Tuesday, so you make Tuesday and Wednesday non-working days.

So, your project calendar has the following information:

  • Working shift for normal days: 4:00 pm to 7:00 pm and for weekends, 9:00 am to 4:00 pm.
  • Non-working days: Tuesday and Wednesday in the second week.

Your project calendar is ready.

You will assign yourself for all the working shifts.

Now you will create a resource calendar.

After cleaning for two days, you will start the painting work on the third day.

You will start painting the ceiling, for which you need a ladder. So, you borrow one from your neighbor for three days. You apply this resource from the 3rd to the 5th day, then you will return the ladder.

On days 13 and 14, your brother is free, and he promised to work with you. You add this information to resource calendar as well.

Now your resource calendar is ready.

Benefits of Using Project Calendars and Resource Calendars

Some benefits of these calendars are as follows:

  • They help you develop a schedule and manage resources.
  • They are also helpful in compressing the project schedule.
  • Smooth resource allocations decrease conflict.
  • They make duration and resource estimation easy.
  • Communication and efficiency is improved.
  • They prevent overloading employees.

Precautions with Project and Resource Calendars

The project environment is dynamic, and there may be some team members leaving or joining throughout. This will affect your resource calendar. Likewise, sometimes you may have to stop work for a day due to a new holiday which will affect your project calendars.

In such situations, you must update the project calendar and resource calendar to reflect the situation. Failing to do so will nullify the effect of having these calendars and conflict will arise due to conflicts in the schedule and resource priority.

You may also hear the term “task calendar.” This is a modified version of the project calendar with tasks inserted into it. Once you create it and apply the resource availability, it becomes a resource calendar. However, since this term is not mentioned in the PMBOK Guide, we will not go into detail about it.


The project calendar and resource calendar are essential documents in project management. Project calendars are about working days, shifts, and times, while resource calendars are about the availability of resources for your project. These two calendars should be updated continuously. If you fail to update, you may experience conflict with resources from other projects, and you may face issues in completing the project.

Do you use project and resource calendars for your project? If yes, please share how they helped manage the project.

Fahad UsmaniGuest Contributor: Fahad Usmani, PMP®, PMI-RMP®, is founder of and the author of A2Z of PMP Certification Exam. He has over 10 years of global portfolio management experience, specializing in leading complex corporate projects. He currently serves as an Inspection Engineer in Kuwait and facilitates project management training programs throughout the Middle-East, and is the founder of PM Study Circle where he writes about project management education and certifications.

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