There's recently been some confusion regarding Seagate's five-year hard drive warranties, specifically with respect to when coverage starts and which drives are eligible. When asked, Seagate offered the following clarification:
A Seagate bare internal hard drive or retail-boxed internal hard drive for PCs or notebooks, sold through authorized channels and by an authorized reseller or retailer, carries a 5-year warranty to the end user. The warranty begins on the date Seagate ships the drive, as is standard practice throughout the industry; in many cases Seagate also adds additional months in warranty protection to allow for the time the product may take to work through channel supply chains before it is bought by an end user.
News source: The Tech Report