[Tom Bunch]

Duration is expressed in terms of the project schedule, always. The help entry on "duration versus effort" explains this but doesn't really clarify why.

The project hours define what hours of the day you normally wish to consider when doing your planning. You can of course have resources come in outside the normal hours, but this period of time doesn't show up on the Gantt chart (unless you turn on View -> Gantt -> Off-hours), and the duration displayed does not account for the time outside of the project schedule. Cost values, of course, do. If you'd like to see this time go by, you should make the project schedule a superset of the resource schedules.

To conveniently give the project a 24/7 schedule while giving your resources a "normal" schedule of 8-12, 1-5, consider putting all your resources into a single resource group and setting up the normal schedule on that group.

You may run into the traditional point of confusion regarding unit conversion factors. Regardless of how many hours of work get done per day in a given schedule, 8 hours is going to be displayed as 1d in duration and effort unless you choose otherwise. This is configured in the Project: Unit Conversions inspector. If you have "Resource 1" come in and work 2 hours of overtime today, they will produce 1d 2h of effort in a single calendar day. It may be clearer if you turn of the display of anything greater than "hours" in the Project: Formats inspector.

-Tom