TOPIC: Critical path diagrams - starting on day xx

I've come across questions on calculating floats and critical paths where some state activities start at Day 0 or Day 1 and some questions doesn't state on what Day it starts. I've also heard that the PMBOK way is starting at Day 1.

What is the ideal strategy of approaching these questions? Is it correct to assume to start at Day 0 unless explicitly stated?

Cornelius has answered this question here: www.project-management-prepcast.com/kune...day-0-or-day-1#23731

Hope that helps.