I have noticed a number of issues with DataSheet/Gantt View when using calculated columns, i will list others at the bottom, however my main concern here is my gantt chart not showing an end date for tasks when the end date is a calculated column.
As you can see in the image I have a "days" column, an "hours" column, a calculated "duration" column (which breaks the hours down into subsets of the day and then adds this to the day) and an "End Date" Column, which is simply [Start Date]+[Duration].
It seems that Sharepoint Online is reading my end date column as blank. (on a side not if i update a task while in the gantt view it will then draw out my bar correctly, however if i leave the page and come back, it will again act as if the end date is blank)
side issues i noticed
I also noticed that though i have a duration column set to 2 decimal places it shows a number of decimal places. (again if i update the task item, this will then revert to 2 decimal places until i leave and return to the page)
I also noticed that my calculated end date column shows as US date format though i am set to UK (and other columns show in UK format)
I have logged a support request with Microsoft, so I will update this with anything useful i learn from them
I am also considering using a workflow to copy the calculated End Date into a standard date column (though this will be a last resort workaround as i don't think you will see the updates until you exit the page and return)
Thanks in advance for any feedback