By Gantt do you mean in the Gantt graph or Gantt columns?
Anyway there is not any supported way to do it with OOTB Duration field however the following workaround could help (or not...)
For Gantt columns: display a calculated attribute, i.e "Real_Duration" with the result of a Datedifference() between task start and finish.
For Graph bars: use the option "Label for bar", which can display a string attribute, this string attribute could have a value from a query lookup and receive the calendar/real duration(finish-start)
harlem-celepar wrote:
By the way, is it possible, to show in the gantt, the Duration by calendar, not in work days? I have a project that need this information.:sad:sad