Understand how dates are used in Project

Microsoft Office Project uses dates to schedule tasks in your project plan. Dates that you enter are used for many purposes, including calculating durations, assigning dates to other tasks, and leveling resource allocations. Because dates are a key aspect of your project plan, you should understand how dates are formatted and how to change that formatting to meet your organization's needs.

What factors influence the calculation of my project's dates?

Project calculates dates based on a number of factors. When you create a new project plan, you enter a project start date. If you don't specify start dates when you enter new tasks, Project uses the project start date by default. The project finish date is calculated based on the latest finish date of the project's tasks.

Tip: To start new tasks on the current date instead of the project start date, click Options on the Tools menu, and then click the Schedule tab. In the New tasks list, click Start on Current Date. When you choose this scheduling option, if you enter tasks without entering dates, the tasks will have a Start No Earlier Than (SNET) constraint applied.

A few of the factors that may affect date calculation include:

  • Duration    Project uses the duration of a task to schedule the task's finish date. For example, if a task starts on November 1 and its duration is 3 days, and if the project or task calendar shows November 1 - 3 as working days, Project calculates the task's finish date as November 3.

  • Resource availability    Resource availability can affect date calculation. For example, if you have a resource that is only available to work 20 hours per week, and you have a task with 40 hours of work that requires that resource's skills, the finish date for the task will be calculated based on that resource's availability. So if the start date for the task is March 12, Project calculates the finish date for 10 working days later, or March 23.

  • Task dependencies    Task dependencies can also affect date calculation. For example, if you have two tasks, and one of them can't start until the other is finished, Project calculates the start date of the second task so that it falls after the finish date of the first task.

Many other factors may influence the dates Project calculates for your project and tasks. Microsoft Office Project 2007 provides the Task Drivers pane to help you identify the factors that are influencing the start date of a task. Find links to more information about the Task Drivers pane in the See also section.

What date and time formats can I use?

Many Project fields accept dates and most date fields accept time information. Project also accepts a wide variety of date and time formats. These date and time formats are based on system date and time formats. For example, if you enter a date as 2/3/07, this will be interpreted as either February 3rd, or March 2nd, depending on the system's regional setting for date and time formats.

You can separate numeric date elements with characters (such as / or -) or a space. For example, for August 14, 2007, you can type 8/14/07, 8-14-07, or 8 14 07.

Note: You can easily change the date format used in your project, and in specific tables in your project. For more information about changing date formats, see the links in the See also section.

The following table shows how Project handles the dates and times you enter:




You can enter the month using the full name, an abbreviation, or a number. For example, you can type August, Aug, or 8.


You can enter a week day using the full name or an abbreviation. For example, you can type Wednesday or Wed. In start and finish fields, Project supplies the full date of the next occurrence of the specified day of the week.

A.M. and P.M.

If you don't include A.M. or P.M. (that is, if you don't type AM or PM) when entering a time, and the default time format is the 12-hour clock, Project sets the time to P.M. unless you enter a value between 7:00 and 11:59, in which case Project sets the time to A.M.

The time format is controlled by Microsoft Windows and is set using Control Panel. For more information about setting time formats, see your Microsoft Windows documentation.

Leading zero

You don't have to type a leading zero before single-digit times. For example, for two o'clock, you can type 2:00 or 02:00.

In many fields, you can type today or tomorrow. Project enters the current date for "today" and the current date plus one day for "tomorrow." You may also be able to type the day of the week, such as Friday. Project enters the date for the first Friday after the current date.

You can enter the time and date in any order. For example, you can type 2:00 PM 8/14/07 or 8/14/07 2:00 PM.

What if my country uses a different date format?

Project displays dates based on your system settings. If your project is currently displaying dates in a format not used by your country, you can change the format using Control Panel. For more information about setting international date formats, see your Microsoft Windows documentation.

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