Hi Glen,
As Gail said, eAudit would make this easy; however, let's examine what is present.
Assets
When you create an asset and save, a record is added to the Asset Move History table (ASSETTRANS). This represents the initial creation date is where there is no Transaction Type.

Job Plans
Each time the JP has a status change, there is a corresponding entry in the Job Plan Status History table (PLUSCJPSTATUS). Therefore, the oldest date with a status of DRAFT is the initial creation date.

PM
Now for the fun one. There is no similar table for the PM as for the other two; however, by default, the PM object is eAudit enabled...and guess what, so does the Asset object. Therefore, all you need to do is create MAXRELATIONSHIP to find the oldest entry.


So, one thing to take away is that eAudit is very valuable and maybe enabled a bit more; however, that has to be taken in the context that it will add rows and, therefore, require more disk space. There have been a lot of times when the value of eAudit outweighs the additional cost. I would counsel that where you do have eAudit enabled that you ensure that you have enabled ALL of the attributes that you want to be recorded in the audit table.
I hope that answers your question.