Wayne from Santa Fe, NM asks: I created a project containing 400 tasks. After entering the tasks I realized that my calendar wasn’t correct and made some changes. I also changed the Calendar options. The changes affected the task durations as well as the assignments and didn’t result in what I was hoping for. What did I do wrong?

Ellen answers: You have discovered a feature that all levels of Microsoft Project have that encourages the user to establish the project calendar and calendar options before entering tasks.

Project provides access to calendars available for use in a project through the “Change Working Time” function. Think of Change Working Time as an access point to the group of calendars that will be available to be used in your project. You can use any calendar as the project, task, or resource calendars. When you adjust a calendar through Change Working Time, you’re not assigning any specific calendar as the project calendar.

To assign a project calendar, for all versions of Microsoft Project click on:

Project | Project Information

Calendar option settings should be specified before entering tasks. If the settings are changed after tasks are entered, the duration values most likely will be affected. These settings are specified for each project. However, in Project 2010 you can set them to be consistent for all new projects.

To view and change the Calendar options for all projects in Project 2010, click on:

File | Options | Schedule

If you’re using an earlier version of Project and you want to view and change calendar options, click on:

Tools | Options | Calendar

The Calendar settings that should be addressed for projects are default start and finish times as well as hours per day, hours per week, and days per month.

The values for default start and finish times are needed to establish the start and finish times of tasks if times aren’t specified. In other words, if the tasks contain relationships, times will be calculated based on the relationships. Tasks might also have a constraint that will specify a time. If neither of those situations exists, this is the time that will be used to schedule a task.

When a task is entered, the values in these option fields will be used to determine the number of hours of work that will occur per day, per week, or number of days per month. The values in the options shouldn’t be changed after tasks have been entered. To see the effect of making these changes, here are some examples.

I’ve entered Task 1 into a project file: