hi,
yes it does matter on van tyres, while the "new" tyres will be in perfect condition, it is easy to forget when they were fitted, plus if you sell the van the new owner " if clued up on this subject" may change them too early, and if you get tyres with a date stamp you can assertain just how long it has been since they were manufactured, and act accordingly.
when I changed mine last year, the tyre fitter brought out some new tyres to fit, I asked what the date stamp was he looked very puzzled but looked er 07.10, so they were already 2years old, I rejected the tyres and he ordered some more, these were 6months old and accepted, if you review the previous threads on this subject you may get a better picture, of the importance.