finding information about tables and databases

Hi -

I'm looking for a variety of info about tables and databases in my 
system (pg 8.1.4, solaris 10).  I'm looking for

1. creation date of a database
2. creation date of a table
3. date of last modification to data in a table
4. date of last modification to the table structure

 From the postings and some testing it seems to me I can get (1) as the 
earliest date of any of the files in the subdirectory of the appropriate 
database oid and (3) from the time of the file as defined by the table oid.

My questions are: how to get (2) and (4), and is there any easier way to 
  get (1) and (2)?

Thanks in advance!