Apologies just experience long time ago I used to look and some Arai dates were 2 yrs ago ...not a issue as long as stored correctly etc....can also invalidate the official 5 yr warrenty I think...
The retailer has to honour the warranty as your contract of sale is with them not arai and for them to haggle over! and warranty is from purchase date not made from date! Otherwise you could lose 2months to 2 years of warranty before you even buy one