Critical Slack Calculation

John,
MSP uses the same unit for the critical slack duration and the task duration; key in task duration in hours to get slack in hours on the gantt chart
Alexandre

I think what John is referring to is the setting under [tools] [options] [calculation]: Task are critical if slack...

I also think the answer is "No"

HTH

John,
if you created resource-constrained schedule then total slacks showed by MS Project are wrong. So it does not make sense to pay attention to these data at all (days or hours - they are wrong in any case).

Yes you are right Vladimir, resource dependencies are just as important as precedence logic, and if you touch the levelling button in MSP, you can be sure that the task flag "critical" means next to nothing.

Assuming John knows this, he could use a formula to drive one of the custom flag fields and then use that flag to mark a Gantt bar as critical based on hourly thresholds rather than the standard days.

I’m out of my territory here but I think in a one-day plant shutdown resource constraints are of lesser concern.