Back calculation of dates in Gantt View

Paul R
Paul R
edited 12/09/19 in Smartsheet Basics

Hi there,

I'm building a schedule in Gantt View by back calculating from an end date. The issue I have (refer attached screenshot) is that I require the finish of the task at row 353 to be the earlier of the start of row 355 or 2 x weeks prior to the start of row 32. When I put in what I understand these predecessor formulas to be, the completion of task 353 is driven only by 2 x weeks prior to the start of task 32, but obviously it should be driven by the start of task 355 (as this is the earlier of the two dates). 

Does anyone know what I am doing wrong here / how to fix it?



Back calculation issue.jpg


  • Isaac Jose
    Isaac Jose Employee

    Hi Paul,

    Thanks for your post, I'm happy to help you with this. It sounds like you're creating a work-back schedule, and you need one of the tasks to finish at the earlier of two start dates. Currently, when multiple predecessors are defined, the dependent date will always occur based on the latest date of the predecessors. For example, in your case, "Final A/W quote" will always finish at the later of your two preceding start dates. If the start of "Upload Due" minus two weeks is a later date than the start of "Place PO," then the "Final A/W quote" will be based on Upload Due.

    The reason for this is in the name "Predecessors." This name implies that Predecessors must occur before the dependent can occur, so all predecessors must be met before, or at an earlier date, than the dependent. 

    Because Smartsheet does not currently support traditional "Successors" for Project Management and dependencies, many people have worked around this by using Start-To-Finish Predecessors to simulate the function of "pseudo-Successors," as would be the case in the development of most work-back schedules. This workaround is effective for simpler projects, but is not a perfect solution as is the case for this instance of a single task with multiple "pseudo-Successors." 

    I've let the product team know that you'd like to see a true Successors feature in our Project Settings and Dependencies, and they will consider it for future development. You can also submit a Product Enhancement Request using the quick link to the right or by following this URL:

    Here are some related articles:

    Since the work-back schedule won't conform to these pseudo-Successors, you could consider creating a traditional work-forward schedule and adjust the Start Dates and Task Durations until the desired End Date is achieved. Alternatively, you can maintain the work-back schedule, setup an alert to notify you when "Final A/W quote," "Upload Due," and "Place PO" start, and manually adjust the duration and lag of these tasks as needed (Alerts and Actions)

    I hope this helps.

    Kind regards,

    Isaac J

    Smartsheet Support