Slack time is an interval that occurs when there are activities that can be completed before the time when they are actually needed. The difference between the scheduled completion date and the required date to meet the critical path is the amount of slack time available. The project manager should always be aware of where slack time exists in a project, since this time can be used to reshuffle the schedule to support the critical path. For example, if there is slack time in a task not located on the critical path, resources can be shifted from that task to tasks located on the critical path, thereby bolstering the most crucial tasks. One can also keep track of the trend in available slack time for each task. If the trend is declining, it can indicate that work is taking longer than expected.