Planning Duration in Decimal Notation

Member for

19 years

yes. In P3, planning unit (duration unit defined for a project) is meant to be the "smallest" unit of measurement for activities in your project. that is why cannot hv decimal.

same case when specifying DAY as the unit of duration, smallest unit is Day. So the question of half-day on Saturday is out the window...

Member for

22 years 7 months

you can try to use planning units in weeks, then in the barchart lalyout try to arrange the scale in months. or else there is no choice to do it. only in MSP(i am not sure about other packages) you can display it like 1.5days or so.