Project 19 is messing with the dates I insert in the task section

[Diony1960]

The task dates seem to change. I have allocated dates and when I put number the predecessor line it alters my dates.. I have started a new project twice and each time the same thing happens I have chosen the start date in the info section. I feel I am doing something very simple but it’s wrong. 

On the column to the left of the task a strange icon has been appearing which is new and I don't understand it. I am setting to auto scheduler but the light blue thumb tack appears over ruling the auto scheduler icon but not all the time.

When I was trying to get the dates right the predecessor number disappears altogether when I with that I can fix the dates and when I re insert the predecessor no the dates skew… also a yellow alert icon appears and that gives me the option to ignore the schedule or force the change of date to the one I wanted.

My heads a bit fried,

[#2 · Accepted solution]

Diony1960,
I'm glad to hear you are using auto-scheduling and saddened to hear you are "allocating dates". If I interpret that correctly, you are manually entering (allocating) dates into the Start and/or Finish fields and that is a big mistake.

The whole purpose of using auto-scheduling is to allow Project's scheduling engine to lay out the plan based on an initial start (Project Start Date), estimated duration for each task, and task relationships (Predecessors). The only time you might manually enter a task's start date is if the task independently starts sometime after the Project Start and those cases should be very rare.

I'm guessing the "strange icon" you see is the little calendar icon indicating the task has a constraint. When dates are entered manually Project sets a "start-no-earlier-than" or a "finish-no-earlier-than" constraint which circumvents Project's ability to create a dynamic schedule.

So, do NOT enter dates (other than the Project Start Date). DO enter task durations, and DO link tasks in a logical sequence. Project will calculate all dates. If the dates are unacceptable, review and modify the plan (e.g. duration and/or task dependencies) until you get what you need.

Hope this helps.
John