one observation: as long as the default calendar matches the project calendar you are using it really does not matter if in fact you are using a global calendar in your schedule. i do not use or recommend global calendars for projects because other users can potentially modify them.

having the shading always being controlled by the default calendar will of course be confusing for anyone who uses many different types of calendars. as a demonstration, i opened up a 5-day workweek project and watched the shading change as i picked different default global calendars.

a potential drawback: many construction projects use more than one calendar. concrete curing, for example, is a 7-day calendar, while the work is ususally a 5-day calendar. the shading can only apply to one calendar and not all the ones being used. the owner might assume based on shading that all activities are governed by a single calendar.

however, since p6 took away our ability to print calendars, this is the only way i know of to show someone the details of the calendar i am using, global or otherwise. for this reason alone i like this shading option.