Start and End date do not align with task duration?

Few days ago one of our client called me and said “There seems to be a bug in Microsoft Project, it is unable to calculate the correct finish date for one of my tasks.” He further added saying “I do not have any constrains or resources assigned to this task yet, but, if I manually calculate the end date for this task, I get a finish date ‘X’, but Microsoft Project is providing ‘Y’ as the end date for this task. The only thing different is that I have a task calendar assigned to this task.”

On further investigation, I noticed the task calendar assigned to this task was a 14hrs a day shift with no holidays. The next step was to check the Project options –

So I opened the project in Microsoft Project Professional and went to File -> Options –> Schedule


As seen above, Microsoft Project uses these setting to convert days to hours.

So let’s say you enter a task duration of 21 days. Project goes ahead and converts the 21 days into 168hrs (21*8 = 168hrs). Now since we have a task calendar assigned to this task that is 14hrs a day with no holidays, Microsoft Project spreads these 168hrs over 14hrs a day which comes out to 12days (168/14 = 12). This is the reason why the dates do not match the duration of the task.

So how to you dodge this curveball??? Well there are essentially 2 options –

· Option 1 – You can go to Project Options and tell Microsoft to use 14hrs instead of 8hrs to convert days to hours, but this will apply for all the tasks in your project, which you probably do not want.

· Option 2 – When you enter the duration for the task, enter it in hours instead of days. So for the above example instead of entering 21days as the duration of the task, you would enter 294hrs (21*14 =294).

Thank you for reading! I hope this helps. Please feel free to comment and let me know if you found this post helpful.