So I contacted 3 nissan dealers.They all said there is no way to know when the belt was produced. 2 of them said 5-8 years is the life span,but if I purchased a new belt,they don't know how long the belt has been in the warehouse.The last 1 said to look at the belt to see if there are any hairline cracks. Don't use it if it has been stored in a humid place.