There have been times when activities in Primavera don’t Start or End on correct dates despite the math saying otherwise . There are several reasons that can cause this to happen, lets look at them in this post.
1) Out of Sequence Activities – These are activities that have started before the predecessor activities are completed. These activities are created when you using “Retained Logic” as your scheduling preference. This creates non-working periods and this can cause the activity to be pushed out of the normal calculated dates. You can check which activities are being pushed Out of Sequence by checking the “Schedule Log”. You can choose “Progress Override” to schedule and correct these dates or change relationships for these activities. For a better explanation on these option check this blog post Scheduling Options – Progressing Activities .