>>So these file dates are a sort of indicator on the possible age of the file, but not 100% reliable.
>
>Would'nt this be a reaonsable risk to take to determin the year - given the circumstances in this thread? Your recommendation?

Just talk to the guys who send these files and try to understand what happens to the files on the way from the source to you. If there's a FTP somewhere along the way, chances are you're getting the transfer date and not the last update datetime on the files. Look at the files you already got and look at their dates. See if there are other date fields in the record, which may be related to this date.

Then use your judgement...