By default Ganib calendar considers.. Saturday and Sunday as weekend( Non-working days) In this was the task duration will be calculated while assigning the task
An it support to manage your own calender using the calendar module.. One can define their own working and non-working days here which will automatically reflects on their tasks duration's.
coming to your question..
to plan a task with in a week end..
Please follow the below steps...
Select Any Project
Click on calender tab
Module Click on Edit Calender
Set the Week end days as "Working time" instead of non-working time
Note: The changes you made with calender will apply for all the task under this project,
you would need to apply the same changes at account level if you want to apply the week end work for all the projects that you have created