Formula to display the duration including holidays

I don't think there is a way round this, the whole point of adding holidays is that it excludes it from claculations as we are usualoly only interested in how many WORKING days there are in an activity. The only workaround I can think of is to use a 7d calendar, however this will also show w/ends which I am assuming you don't want - otherwise you would likely have already done this!

Using Spider Project we just use a Date Function to create the desired formula.

I agree with Paul, the whole point of adding holidays is that it excludes it from calculations as we are usually only interested in how many WORKING days there are in an activity.

Because working with formula can be time consuming when the focus is on a few activities creating a hammock can be a good option as you can toggle the hammock calendar and investigate the duration changes.

Also, if your software does not support such a formula then the hammock can still give you what you want.

If you want to investigate impact of lag calendars using a similar approach just create your hammocks linked to predecessor and successor and toggle the calendar.

I suggest doing what-if using a separate project file.

Best Regards, Rafael

It is not unusual for CPM Schedules to have multiple calendars. Shift Work Weeks and Odd Work Weeks (when work hours per day are not all the same) although rare, do happen. In some cases, it might be that contract restrict work hours to be at different hour on different days, I have seen such restrictions in hospital works. Other times some resources work on alternate weeks such as work at offshore platforms. The need for multiple calendars is real, not accounting for multiple calendars when they happen can(will) yield unfeasible schedules.

Because displaying Duration Days only can be misleading many schedulers also display hours. I like to keep a layout that display Duration Days, Duration Hours as well as Duration Work Days, none of which require complex formulas.

Sometimes a layout showing bars detailed by hours is convenient as it will catch any calendar exception.

Looking only at days is not good enough.