I believe that I explain this as part of the lesson of The PM Podcast. Both formulas are correct. But there is a difference in "philosophy" behind them.
* If you follow my formulas (with the '-1'), then you assume that your project begins on "Day 1"
* If you follow the other formulas, then you assume that your project begins on "Day 0"
I prefer my formulas for 2 reasons:
* If your boss tells you that your project begins on the first day of the next month, then he means "January 1" and not "January 0"
* All modern scheduling tools by default start on day 1 and not on day 0 (mainly because they are calendar based)
That's really all there is to it.
Until Next Time,
Cornelius Fichtner, PMP, CSM
President, OSP International LLC
Moderators: Yolanda Mabutas, Ahmed Amin, Scott Gillard, Mary Kathrine Padua, ERIC BARTLETT, Gail Freedman, Kevin Nason, Steven Mudrinich, PMP, Mark Wuenscher, PMP, John Wolverton, Tracy Shagnea, PMP, Jada Garrett
This interview with Simona Fallavollita (LinkedIn Profile) was recorded at the magnificient Project Management Institute (PMI)® Global Conference 2017 in Chicago, Illinois. We discuss the how, what, why and when of the changes that are coming to the PMP exam.