TOPIC: Day 0 or Day 1 Calculations for Float?

If the question doesnt explicitly mentioned day 1 or day 0 to be used, what should you consider in calculations?

One way is to look at answers and find out using elimination.
But what you have answers for both day 0 and day 1 formula?
How do you calculate? Will PMI exam have such 1 day difference answer formulas?

If you need to use one or the other to arrive at the correct answer the question will tell you which one to use. In my experience I was always free to use whichever method I wanted.