I would say no formula is needed for that .. say if you start your activity at day 1 and finish on day 1 .. duration will be 1 day not 0 day. So you have to add a day if you use subtraction method.

I would say what PM Prep Case suggested is right.

I have same confusion and infact our confusion are correct as illustrated by your example we get different answers by different methods which means one of the method is incorrect.
-Sagar

Please read the explanation about 0 / 1 start date in our knowledge base at the following URL:

www.pmhelpdesk.com/entries/20346821-why-...ting-es-ef-ls-and-lf

Please can anybody answer the question because I am also confusing.

Rita follows 0 start and you follow 1 start. What is the correct for the exam?

Thank you

I have recently purchased the PMP® Exam Formula Study Guide, which is helping me to identify gaps.
My question is on Network Diagram, while many claims the first activity early start can neither be 0 or 1 & the corresponding results will be the same on either methods. Iam following to adapt 0 days for easy calculation.Which is the correct method & easy to understand?
I would like to mention the one of the question & answer provided in your kit.
Question : The activity “Ship Container” in your network diagram has an early
start of day 17, a late start of day 22 and a late finish of day 37. What is the activity duration?
A.) 15 days
B.) 16 days - Correct Answer
C.) 59 days
D.) 14 days

Based on the Formula guide the formula says Activity Duration=EF - ES + 1 or LF - LS + 1..when translated AD= 37-22+1 = 16. Since iam following "0" to be the ES of my activity my answer would be 15.

This may be the most silly question, but kindly clarify.