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Late Start and Late Finish earlier than Early Start and Early Finish

10 replies [Last post]
Rachel Dorota
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Dear all,

In a schedule that I used the same calendar for all the activities I experienced the fact that for some activities on critical path the late dates were earlier than the early dates.

e.g. ES:1-MAR-2014 LS:28-FEB-2014 late start one day before the early start, while what I expected was to happen the same day 1MAR2014.

 

Any ideas?

Replies

Raymund de Laza
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Joined: 23 Nov 2009
Posts: 698

Ronald,

Thanks for the Info.

I noticed in P6 that Late Dates are blanked out when selecting a Progressed Override or Actual Dates. Retained Logic will show the Values of those Late Dates.

 

 

Regards,

Ronald Winter
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Raymund,

That is not a ‘bug’ but a feature.  Correct CPM calculations require that all activities in the network be considered in the computational process, even completed ones.  You are just used to seeing the columns blanked-out after the computatins are made and mistake that for a fact.  P3 blanked-out the columns, so one believes that the dates do not exist. 

P6 used to blank out the computed dates for completed activities after making the CPM calculations until one day I happened to be talking to Joel Koppleman (Primavera co-founder) complaining about this.  He was unaware that P6 was doing this and said that he would look into it.  P6 Version 5 came out and the computed dates were there for all to see.  It has (correctly) been that way ever since.  Have a great day!

Raymund de Laza
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Posts: 698

Gary,

Agreed with you that out of sequence is one of the factor having a negative float.

This is the same bug as late dates are still appearing even the activities are in progress or completed.

 

Regards,

Ronald Winter
User offline. Last seen 5 years 22 weeks ago. Offline
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GAry,

You reminded me that using the Actual Dates calculation method can cause negative float. 

Mike Testro
User offline. Last seen 1 week 4 hours ago. Offline
Joined: 14 Dec 2005
Posts: 4393

Hi Gary

Irregular calandars will cause negative float.

Best regards

Mike Testro

Gary Whitehead
User offline. Last seen 15 weeks 2 days ago. Offline

Other than constraints, the only 2 causes of negative float I am aware of are external relationships and out of sequence working.

Raymund de Laza
User offline. Last seen 13 hours 19 min ago. Offline
Joined: 23 Nov 2009
Posts: 698

Ronald,

My project was constraint to Project Must Finish By date but I encountered in a part of my Schedule I had afew activities with negative float despite the Project Finish date is equal to Constraint Date (Date and Time).

There are no external relationships and external dates. The only constraint is the Project Must Finish Date.

What are other Possibilities having the negative Float?

 

Regards,

 

Raymund

Ronald Winter
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Really?  Not even a Project Must Finish By date?

Rachel Dorota
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I did not use any constraint...

Raymund de Laza
User offline. Last seen 13 hours 19 min ago. Offline
Joined: 23 Nov 2009
Posts: 698

Probability due to presence of Constraints along the path.