Looking at this further I notice that there doesn't appear to be any kind of format version number in the header info. Shame on your source for that. But even so, it appears to a simple matter to just check to see if the Date/Time header is present in the first header line and if not you know you are dealing with (what I presume is) the newer data format.
On a side note, this kind of data format has been largely replaced by XML for B2B data exchange. Some vendors have opted for a CSV format, but it is just simply amazing to see how many programmers can not generate a proper CSV file, or an XML file for that matter. There is still something to be said for a fixed length record after all. :)
On time, cheap, compliant with final specs. Pick two.