How to understand the way MailStream Plus populates the date in the SEG-1150 if the xx INF with SADSAM is not present

Product Feature: General
MSP 8.3.2 is current version
Operating System: ALL Platforms

How does the date get populated for the Mail.dat Field Code SEG-1150?  The MailStream Plus (MSP) job is not using:
xx INF with the subkeyword  SADSAM
But a date is being populated in the SEG-1150.

This information is being pulled from the USPS Postal Reference files.  For example, here is the date found in the msrprpt/jobname.rpt/prntrpt  using the MSP Sep 2016 Postal Reference files:
Postal Reference File Build Date                             SEP16
Delivery Count Dates
    Publication Date                                         2016/09/01
The RP INF with SADSAM can be used if you want to change this date.  Otherwise, it will use the date from the Delivery Count Publication Date.
UPDATED:  August 14, 2017