How to assess impact of overtime on a project

Copper Contributor

I have set up what I think is a relatively simple 2013 project using the default settings. I start with some manually scheduled milestones at the beginning followed by a bunch of auto-scheduled tasks. I have 5 people on a team, and each person can work any task so I set up one resource that maxes out at 500%.


I now need to see what the impact to the project end date would be if everyone worked 50 hours per week rather than the default 40. I go into Project Options - Schedule and change Hours per day and Hours per week to 10 and 50, respectively. The auto-scheduled task durations change as expected (i.e. a 5 day task reduces to 4 days), but the start and finish dates do not (they still represent the original 40hr/wk timeline). Also, after changing the default hours per day and week, if I go manually change the duration the start and finish dates no longer update like they did prior to changing the hours per day/wk. Any idea what happened and how I can get the desired result (which is to shorten the project length by working more hours)?

4 Replies
First question, why did you set up manually scheduled milestones? To get the most help from Project's scheduling engine, all tasks, including milestones, should be auto-scheduled.

I see nothing in your description about creating a custom calendar for the 10 hour workday. Without that, the start and finish dates won't change. For reference, it's bad practice to modify the built-in calendars (e.g. Standard) directly, custom calendars should be separately created although they may be based on one of the built-in calendars.




Hi John,


Thank you for the reply. I'm relatively new to Project so I'm kind of learning as I go. I used manually scheduled milestones to represent when data would be available for my team to begin working with. The dates for when the data become available are fixed and independent of the rest of the project. Is there a better way to represent this?


I didn't put anything in my description about creating a custom calendar because, well, I didn't create one. It sounds like that might be the missing link. I'll try creating one, applying it to the resource, and see if that works. Will report back if that solves my issues. Thank you for the tip!

Good news for me: In terms of the overall schedule and the impact on the project end date, creating and applying a custom calendar seems to have had the desired effect: I created a copy of the standard calendar, changed the working times to reflect a 10hr day, and applied that to the resource. The start and end dates for each task were shortened, as was the overall project length. Interestingly enough, though, the duration of each task remains the same (even though the start and finish dates now reflect a shorter duration, which I find confusing). I suspect this is because the custom calendar is applied only to the resource and not the task.

Even though you suggested modifying the default calendar is not good practice, I tried combining these two things (modifying the base calendar to 10hrs/day, and applying the custom 10hr/day calendar to the resource) and the desired effect has been achieved: the duration for each task is shortened, the start and finish dates reflect the shorter duration, and the overall length of the project is reduced.

Although this is working, I wonder if there is a better way? Again, greatly appreciate the help.
best response confirmed by db8673 (Copper Contributor)
There are three levels of calendar in Project. The Project calendar (Project > Properties group > Project Information) is the "master", all resources and tasks follow that calendar unless changed by the next two items. The project calendar is represented by a "none" in the Task Calendar field when added as a column in the Gantt Chart view.

A task can have a separate calendar and that is set either via the Task Calendar field (Gantt Chart view) or in the Advanced tab of the Task Information window.

A custom resource calendar is created by selecting the resource (e.g. Resource Sheet) and then selecting Project > Properties group > Change working time. Once a custom resource calendar is created, select it as the Base Calendar for that resource. Unlike tasks, the default Base Calendar for resources is directly specified (e.g. Standard) rather than simply showing "none" as is the case with tasks.

You can see custom project and task calendars when you look at the Calendars tab of the Organizer but you will NOT see custom resource calendars.

Unless most of your tasks or resources follow the Standard calendar, I suggest you make your custom 10h day custom calendar as the project calendar. That covers everything but, if you need further customization of work days/times for tasks and/or resources, create and apply those as noted above.