I have two tasks in ms project:

Task A, start: today 03/22/2017
Task B, predecessor: Task A FS+12eMonths
Task A and B are both 0 days long and automatically planned.
Task B start/finish is calculated: Saturday, 03/17/2018

Question 1: Why?
Question 2: What field or project settings would I have to use to achieve the date which I would expect (03/22/2018), without setting it to a manual field?


1 Answer 1


Microsoft seems to have hard-coded 1 emo = 30 edays. There is no setting to achieve your expected date, which is based on the variable human interpretation of "month." For workarounds, I would definitely stay away from task mode (i.e. "Manually-scheduled"). You could play with task calendars and/or constraints to force the second task to the date you expect. In the long run, users of CPM scheduling tools like MSP need to give up on such expectations altogether.

  • Thanks for explaining. How would you add a bunch of tasks which definitely take 10 months or 15 months? You won't calculate them on your own or would you?
    – Peter
    Mar 22, 2017 at 16:41
  • I would simply stay away from using months as a unit of time measurement in a project schedule. Work time is paramount, and calendar months do not have a consistent amount of working time. Use weeks or days.
    – Tom Boyle
    Mar 23, 2017 at 0:45

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