Hi,
We are implementing Redmine in our organisation and we track delay in any issue on the basis on the basis of number of days it has been delayed i.e difference between actual date of completion and scheduled due date.

What I figured out is this feature is missing in Redmine. I request you to add this feature and the delay should also be reflected in gantt chart on the basis of days. It would be better to if its added because we don't track on the basis of no of hours spent.