You are attempting to use a PUT where you need to be using an INPUT. The code you have shared is reading up your "date-string" as character with the specified INFORMAT in your INPUT statement.
To convert that character string to a SAS numeric DATE variable, you need to use the INPUT function with the specific INFORMAT based on the string.
Also, with your INFILE statement, you may want to explore whether or not the DSD parameter may be needed, if you might have null input fields to read up.
Scott Barry
SBBWorks, Inc.
Step-by-Step Programming with Base SAS Software, Working with Dates in the SAS System
http://support.sas.com/documentation/cdl/en/basess/58133/HTML/default/a001304321.htm
SAS Language Reference: Dictionary, Informats
http://support.sas.com/documentation/cdl/en/lrdict/62618/HTML/default/a000309877.htm