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When using Start-Finish Predecessors, tasks are ending at start of next day instead of end of the day RRS feed

  • Question

  • Hello all.

    We schedule projects both from a start date calculating forward and from a finish date calculating backwards.

    When using a start date, the calculated start and end date/times are what I expect.

    However, when I use the finish date the finish dated on every task is incorrect.  More specifically, the time is wrong.  Instead of finishing at the end of the day, it finishes at the start of the next day.

    There is a simple example below.  In this example, each task has a duration of 1w.  In the first set of tasks, I plan from a start date.  Each task starts on a Monday at 8:00AM and ends on the next Friday at 5:00pm.  That's perfect.

    In the second set of tasks, I plan from a finish date.  Each task starts on a monday at 8:00AM (good), but ends the following Monday at 8:00am.  This is a big problem because we usually only display dates, not times, so it looks like we have 6 days to complete each of those tasks. (Note: we use project server, so resources see their assignments on the web app and the end dates are wrong).

    Has anyone else seen this?  Is there something I can do to correct it?


    Thanks, Craig



    • Edited by CraigS99 Wednesday, October 30, 2013 2:08 PM
    Wednesday, October 30, 2013 2:07 PM

Answers

  • Craig,

    Not wishing to encourage your use of reverse scheduling, as I dislike it as much as some of the others who have weighed in on this topic.  However, you may have found a genuine bug in way that Project handles the dates/times for reverse scheduled tasks.  That 8:00AM Finish time on some of the tasks just does not seem right.

    Meanwhile, I have a work-around to suggest.  Here is the result:

    I've created a new custom field (Finish 1) and used the following formula:

       ProjDateAdd([Start],[Duration])

    In the illustration the heading is Finish (Revised) and--as you see--I can get the dates (on the reverse scheduled tasks) to match those on the forward scheduled tasks.

    I hope this help you out.



    • Edited by Edward Hanna Saturday, November 2, 2013 12:33 AM Remove signature
    • Marked as answer by CraigS99 Monday, November 4, 2013 2:56 PM
    Saturday, November 2, 2013 12:33 AM

All replies

  • Craig,

    I see your point. You have found one of the good reasons not to use reverse scheduling. My suggestions are:

    1. If you insist on using reverse scheduling, live with the dates & times as displayed. If you look at the timescaled work, you will see that no effort is shown for the finish time of 8:00 am. It correctly "begins" at the end of the day, in your case the previous Friday. Now I know you are not assigning resources, but this demonstrates that what you see in the Start and Finish fields is really just a display quirk

    2. Use a custom Finish field with the following formula to "correct" the finish date, and time. The formula will work correctly for both forward and reverse scheduled tasks. You could even set up the Gantt bar to use the Start and Finish1 fields as the end points for the bar

    Finish1 = ProjDateAdd((ProjDateSub([Finish],"1d")),"1d")

    3. Don't use reverse scheduling at all. Instead use normal forward scheduling and use either a deadline or a finish-no-later-than constraint on the last task in the sequence. It's just a lot easier for humans to think in forward scheduling mode anyway.

    Hope this helps.

    John


    • Edited by John - Project Thursday, October 31, 2013 1:50 AM add formula
    Wednesday, October 30, 2013 4:00 PM
  • Hi,

    Just a reminder that to obtain the backward pass dates you don't need to change anything, just display Late start and late finish.

    Greetings,

    Wednesday, October 30, 2013 7:16 PM
    Moderator
  • Jan,

    I'm sure I'm missing something but when I tried that the late finish date for task 10 in the example above, shows as 11/8/13 5:00 PM. If I use the Early Finish field, it shows 11/4/13 8:00 AM, same as the Finish field.

    John

    Wednesday, October 30, 2013 8:01 PM
  • It's doing what you told it to do (i.e. Finish when the logical Predecessor Starts).  So, #10 Finishes exactly when #11 Starts.  But I do understand your issue with the Finish date displayed.

    Here's a work-around.  Change the Predecessor value for Task #10 to: 11SF-1 min.  This will "fix" the Finish dates on #10 and all of its Predecessors.  Since you only display dates--not times--all should be well with the Finish dates.

    Of course, test for unwanted side-effects before proceeding (e.g. what impact on Duration).




    • Edited by Edward Hanna Thursday, October 31, 2013 12:53 AM Remove signature
    Thursday, October 31, 2013 12:52 AM
  • Thanks everyone for the input.  A couple comments:

    1.  Reverse scheduling is something that I do quite often.  If the only solution is to not do it, I will be very dissappointed.

    2.  I can't use a calcualted field because it will not work when I plan forward (we do both)

    3.  The 'Late Finish' Idea does not seem to work.  I also get 11/1/13 as the Late Finsih for all tasks

    4.  I don't agree that it is working as it should.  In the first example, we are using Finish-to-start relationship and it's smart enough to start the preceeding task on the next minute, not the same minute.  Start-to-finish should work the same way as finish-to-start (just reveresed).  The software should work consistently.

    5.  Using the 11SF-1 Min does not work either.  When I do that, the start date changes from Monday at 8am to Friday at 4:59PM.

    Any other thoughts?


    Thanks, Craig

    Thursday, October 31, 2013 7:24 PM
  • Craig,

    For item 2, the formula I gave you works for both forward and reverse scheduled tasks. I tried it before I posted. Did you actually try it? If it didn't work for you, please elaborate with an example so I can understand why you think it doesn't work.

    I was hoping Jan would respond about the early and late idea, they don't appear to resolve the display issue you raised so I'm thinking he may have misread the question.

    I agree, Project doesn't appear to be working as it should with regard to dates and Gantt display for reverse scheduled tasks. Project is not consistent in the way it presents the data, at least as far as I can tell. Before I posted my response I also tried it in Project 2007 and unfortunately it does the same thing. I never noticed it before probably because I never use reverse scheduling.

    I didn't actually try Edward's suggestion about using 11SF - 1 minute. On the surface it would seem to skew the data by 1 minute. I guess he will have to respond on that.

    Meanwhile, you said that you use reverse scheduling quite often. Project does some strange things in reverse schedule mode, at least they appear to be incorrect because we are used to thinking in forward scheduling mode. I would venture a guess that the vast majority of project managers use forward scheduling simply because it is more intuitive. If you want to use reverse scheduling and forward scheduling I would not mix the two in a single schedule. As you can see, you will end up with a whole lot of confusion particularly if you have to show or explain the plan to others.

    My thoughts.

    John

    Thursday, October 31, 2013 9:20 PM
  • Hi,

    OK, my post may have been a little short.

    It didn't explicitly say DO NOT USE SF LINKS (IMHO SF stands for Science fiction) especially if you do not agree to the way Project calculates them.

    It should also say don't invent any fancy links or anything to have backward pass calculated. Project does that automatically and correctly for you.

    So completely forget tasks 7-11. There is absolutely no need for them.

    Now show Late start and late finish. They give dates and times you want.

    Greetings,

    Friday, November 1, 2013 8:45 AM
    Moderator
  • Science Fiction!  LOL.

    I must be missing something.  I added Late Start and Late Finish and this is what I see, how does that help?


    Thanks, Craig

    Friday, November 1, 2013 5:52 PM
  • Hi,

    I'm shocked to see that you still show the lower 5 tasks. Aren't the late start and late finish of the first 5 teasks exactly what you called "This is what I expect" in your first post? If you want to see the difference between early and late set a Must Finish On on task 4.

    How does this help? It's whet you asked for, that's all.

    Greetings,

    Friday, November 1, 2013 6:53 PM
    Moderator
  • Hello.

    Sorry, obviously I was not clear.  What i want is the same finish dates for task 8-10 (reverse scheduling) as the finish tasks for tasks 2-6 (forward scheduling).


    Thanks, Craig

    Friday, November 1, 2013 8:19 PM
  • Hi Craig,

    Since we are on the "I wan" now, I want you to use Project's reverse scheduling (i.e. reading Late Start and Late Finish) and not try to invent one of your own. The one you invent doesn't work exactly as you want - pity. The one Project does for you works. So far so good. Do you want a result or do you want to reinvent Project? Your choice.

    Greetings,

    Friday, November 1, 2013 9:32 PM
    Moderator
  • Craig,

    Not wishing to encourage your use of reverse scheduling, as I dislike it as much as some of the others who have weighed in on this topic.  However, you may have found a genuine bug in way that Project handles the dates/times for reverse scheduled tasks.  That 8:00AM Finish time on some of the tasks just does not seem right.

    Meanwhile, I have a work-around to suggest.  Here is the result:

    I've created a new custom field (Finish 1) and used the following formula:

       ProjDateAdd([Start],[Duration])

    In the illustration the heading is Finish (Revised) and--as you see--I can get the dates (on the reverse scheduled tasks) to match those on the forward scheduled tasks.

    I hope this help you out.



    • Edited by Edward Hanna Saturday, November 2, 2013 12:33 AM Remove signature
    • Marked as answer by CraigS99 Monday, November 4, 2013 2:56 PM
    Saturday, November 2, 2013 12:33 AM
  • Jan:

    I didn't think I was inventing a new way to schedule.  However, if there is a better way to reverse schedule, I'm all ears.  Simplying using Late Start and Late Finish does not give the correct dates (per my example above).  Is there a link you can point me to that describes how to create a schedule backwards from a finish date?  Or show me a quick example?

    Ed:

    Thanks.  That will certainly work, but will be very difficult to implement in our environment.  We have hundreds of projects in project server and every project must be consistant.  This will take some training and a lot of work, but it looks like it might be my only option.

    Thanks everyone for your input


    Thanks, Craig

    Monday, November 4, 2013 2:56 PM
  • Hi,

    "All ears"? I wrote twice that Project iself, natively, without extra effort, always, inevitably, also does reverse scheduling and puts the result in Late Start and Late Finish. Didn't you hear it? Stop looking for "an alternative way": it's there.

    By all means, open

    http://users.online.be/prom-ade/Backward.mpp

    Is this reverse scheduling or what? Moreover it uses 17:00 and not 8:00 so it answers your question.

    Greetings,

    Wednesday, November 6, 2013 8:45 AM
    Moderator