 <p>While not explicitly documented for the <a href="http://docs.aws.amazon.com/AWSEC2/latest/APIReference/ApiReference-query-DescribeSpotPriceHistory.html" rel="nofollow">DescribeSpotPriceHistory</a> API action, this restriction is at least mentioned for the <a href="http://aws.amazon.com/console/" rel="nofollow">AWS Management Console</a> (which uses that API in turn), see <a href="http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/using-spot-instances-history.html" rel="nofollow">Viewing Spot Price History</a>:</p> <blockquote> <p>You can view the Spot Price history over a period from one to 90 days based on the instance type, the operating system you want the instance to run on, the time period, and the Availability Zone in which it will be launched.</p> </blockquote> <ul> <li>Since anybody could have retrieved and logged the entire spot price history ever since this API is available (and without a doubt quite some users and researchers have done just that; even the AWS blog listed some dedicated <a href="http://aws.typepad.com/aws/2009/12/thirdparty-aws-tracking-sites.html" rel="nofollow">Third-Party AWS Tracking Sites</a>, but these are all defunct at first sight), this restriction admittedly seems a bit arbitrary, but is certainly pragmatic from a strictly operational point of view, i.e. you have all the information you need to base future bids upon (esp. given AWS has only ever reduced prices so far, and regularly does so in fact much to the delight of its customers).</li> </ul> <p>Likewise there's no option to change the frequency, so you'd need to resort to client side code for the hourly aggregation.</p>