When you enter "6 days" as the duration, that means the task will require 6
working days to complete. The calendar option "hours per day" setting
defines how many hours you mean when you use the word "day" in a duration.
The working time calendar defines which hours out of the day count towards
burning up those hours of work required to complete the task. With
everything as the default, if a task is 6 days duration, that means 48
working hours are required to complete it. If a resource works 8 hours per
day, and starts Monday at 8am, he will finish 48 hours of work the following
Monday at 5 pm. But if you give it to a resource who only works part-time,
4 hours per day, it will take him twice as many working day to complete the
required 48 hour of work. The duration will still read "6 days" but the
start and end dates would now be almost 3 weeks apart according to the
Presto Sparkplug calendar on the wall.