Do you have a picture of the side of the filter? So we can see the media?
2004 could mean the 20th week of 2004 or the 4th week of 2020
The date code is probably more specific than just the year.
Looking at the application guide on Manns website for that filter, it doesnt fit any vehicle built before 2013. Highly doubt that Mann had that filter sitting on a shelf for 9 years before a car that used it rolled off the assembly line
anyway i fired up an email to mann about this. hopefully they'll reply.
finally mann turkey replied:
in short: 2004 is not the year but it is 2020/04
phew