Okay, just went through the shipment and papers: There's nowhere a note to be found regarding a reduced warranty period. So I guess european legislation is valid here that grants the consumer a limited 2-year warranty (which of course I already voided anyway )...
To my knowledge there is no way around the two year warranty for new goods (within the EU). OK, after 6 Months it can be interesting to argue as the end-user has to prove that the problem already existed from the beginning. But that highly depends on the seller. Because not the manufacturer but the seller has to cover this warranty. But this looks different outside the EU.
If the manufacturer offers other time spans (e.g. 90 days) this does not shorten this 24 month warranty. But it could be other way around (e.g. some manufacturer offer 5 years for cash or even for free). So the 90 days do not really apply in the EU but in other regions that could make the difference.
At least that's my understanding.