MS Project 2010 End Date Calculation

Question

Good Day

I am just testing out how MS Project deals with holidays and I'm finding that there is a difference between manually calculating dates and the way MS Project calculates, so obviously I'm missing something here.

I have one task with no resources assigned, and I have modified the Standard Calendar to include 27 holidays. The time period is to be scheduled from 2015/11/30 (30 November 2015) and the duration should be 36 weeks. Then, I want the end date to be calculated.

My working days are typically from 08:00 - 17:00 with 1 hour for lunch, with 5 working days in a week (weekends have been excluded) @ 8 actual working hours per day. 

What I want MS Project to do, is to literally add 36 weeks to 30 November 2015, and then add another 27 days for the holidays. However, when I just schedule the task, by specifying the start date and duration, I get the wrong end date. I get 2016/09/14, instead of the expected 2016/10/07.

What am I missing here?

Kind Regards

Answer 1

What is the basis of your expectation of 7Oct'16 as the finish date?

Issues of clock time and calendars aside, if I start the morning of 30Nov'15 and add (in elapsed/calendar days) -- 36 weeks (252edays) and 5 weeks plus two more days (37edays) to account for your 27 holidays -- then I arrive at the morning of 14Sep'16.  (In "calendar math" this is the same as the evening of 13Sep'16.)

I get precisely the same result  (i.e. ending at 17:00 on 13Sep'16) by adding 27 workday exceptions to a default "Standard" (5dx8h) calendar and assigning it to a single task of duration = 36 weeks (using all default hour/day/week/month definitions).  Your date of the 14th may be explained by changing your display preferences to include time of day.

Answer 2

Yes, my apologies. For some reason in my brain 36 weeks = 9 calendar months. Which is not true.

Thank you for the logic.