One of the key features missing from a relational data tool such as SQL Server is built-in Time Intelligence. SQL Analysis Services and PerformancePoint Server are 2 tools where time intelligence and analysis of historical data are simplified and available out-of-the-box.
Time Intelligence filters within PerformancePoint provide users with a way of specifying dates using everyday terms like Today, Yesterday, Last 6 months etc rather than having to select from a calendar control or pick different measures/metrics.
David Francis Blog
At its simplest, the PerformancePoint implementation of time intelligence filters are really just MDX generators, simplifying MDX for the end-user.
David's blog recaps this nicely.