Planning back from an end date
 

I'm trying to create a plan that has a fixed end date that we must hit. I need to have Omniplan build the gant chart back from that end date, not forward from a start date. Is there a way to do that?

I'm pretty new to using Omniplan, but I'd image you could set your last task to have an end-date constraint and then connect your last task and second-to-last task from Finish to Start.

What you need to make this work conveniently for a plan of any substantial complexity is the ability to tell OmniPlan to schedule the start date of tasks to "As late as possible" instead of "As early as possible" but unfortunately that option doesn't exist in the shipping software. You should be sure to send in a request for the feature using Help->Send Feedback if you want it!

In the meantime, OmniPlan can help you figure out the dates on the critical path. Build up your plan outline, put a milestone in for the end with constraints set to the date you must be finished. Put in a start date for the project that is well before when you can actually start the project. Try to do as little setting of explicit dates as possible — you should do this only for actual fixed dates, with everything else being determined by resource availability and ordering dependencies (Joe can't start this task until he finishes that other task). Now you can adjust the start date of the project via the inspector and see when all the violation flags start appearing because there's no longer enough time to complete the tasks as ordered before the deadline. Hopefully the proposed project start date where that happens is in the future :-)