We are in the process industry. In one of the logistics company, I am typically facing w.r.t. Planned Start Date after running regenerative MRP. (MPS not implemented)

Forecast Period - Feb 2009
In some of the manufactured items the Planned Start Date for Planned Production Batches are going back to 05.01.2006 for all the production batches it has generated (same starting date). However, the end date is coming to be alright. I have checked following parameters.

Lead time/Safety time in Item Master including containerized
All dates in formula master & BOM (Maintain Materials)
Calendar
Work Centre, Task, Routings
Rechecked cycle time
Any Open Orders for previous period

I have tried all possible ways to find out the reasoning as well as this particular date appearing in any of the masters.

Out of 7 items for MRP generated 3 items are creating this problem and rest 4 items are coming okay with start and end date correctly.

Can anybody immediately help !

Not sure if this will help but I have found the following:
My query related to finding which fields were responsible for calculating the start date of a production & purchase order.
Manufactured MPS Item - Work Centre Resource Unit hr/day, Task Prod Rate, W/C wait time, Item master Order interval & safety time.
MRP Purchase Order - Order Interval, Item master order lead time, Item master safety time
MRP Manufactured Item - Order Interval, Item Master safety time, resource unit hr/day, production rate & safety time
MRP Purchase schedule - Frozen period, Order interval, safety time

Yes, I have found out the solution. That is very much b'cause of WC planning hour rate defined. In the specific WC, instead of 24hr working, it was defined as 1 hour.

thanks