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MS Project: How can I find number of days between project start date and task start date in MS Project

Kamal settled down, opened his laptop and said “Whatever I am learning here, I started applying most of the things in my project planning. My management is happy to see that things are getting more manageable now”.

“However, my manager want to know few things how it happens in MS Project” he continued, “How can I find number of days between project start date and task start date?”

He opened KidVentures.in case study and pointed what he wants.


For example difference between project start date is July 1, 2015 and a task ‘Develop Code’ start date August 14, 2015.

Yes, finding the difference between project start date and task start is possible with minor customization. There should be a custom field created to calculate and show that information for the user.

Following are the steps to achieve it.

Step 1: Go to Project Tab

Step 2: Click on custom fields

Step 3: Click task radio button

Step 4:  Select Type as duration


Step 5: Select any given duration field and rename it (e.g change Duration10 to MyDateDiff)

Step 6: Click formula button in custom attributes

Step 7: Enter formula as given below

ProjDateDiff([Project Start],[Start],[Project Calendar])


Step 8: Click ok

Step 9: Go to Gantt chart and add this custom field.


Step 10: Now this column shows the difference between the project start date and task start date for each task in the new column.


Take a closure look at the formula used ProjDateDiff([Project Start],[Start],[Project Calendar])

ProjDateDiff is function that gives the resultant in number of days that is equal to difference between two dates as according to selected calendar.

[Project Start] represents project start date.

[Start] represents task start date.

[Project Calendar] represents Calendar selected for project, e.g. standard calendar


Aforementioned formula can be changed based on the difference between dates user wants. e.g. If project is already baselined, then user may want to consider baseline start date of task instead of task start date. Now the formula becomes ProjDateDiff([Project Start],[Baseline Start],[Project Calendar])

If user wants to build new formula, then user can use the buttons, fields and function as accordingly.


Kamal appeared in next day class with all smiles and mentioned his manager was so happy to see management expectations addressed through this solution.

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