What kind of 'date' field validation is done in general in MailStream Plus?

In general, MailStream Plus (MSP) only checks date fields for the month being between 1-12, and the day being between 1-31.  MSP does not know how many days are in each month or leap years, etc.  
So a date such as 11/31/2015 would be considered 'valid', even though there are only 30 days in November.  
A date field that has a month or day outside of the valid 1-12 or 1-31 range is considered invalid.

For the MDMFSD Induction Date validation-
First the date is checked to see if it is valid within the 1-12 and 1-31 ranges.  If not, then you get a message that the date was not used for validating the induction date, (i.e because the date was deemed invalid, the message will say that a valid date for the MDMFSD Induction date field was 'missing')-
"The PRF Mail Induction Date Validation not done due to Missing INF MDMFSD"  

If the date is considered valid, then the date is actually checked against the 2-month range of dates that the Postal Reference Files (PRFs) being used are valid for.  
For example, the September 2015 PRFs are valid for mailings dropping from Oct 1 2015 thru the actual date Nov 30 2015.
If the MDMFSD date was 11/31/2015,  that is past the valid end date for the PRF files, so even though there is no 'Nov 31' MSP would end with the message-
"The Mail Induction Date is out of Range for the PRF due to Value of INF MDMFSD."
And of course any date after that (say in December) would be out of range also.
UPDATED:  April 28, 2017