Define a time dimension
This rule analyzes databases to determine whether each database contains a time dimension.
You should specify a time dimension.
To identify a dimension as a time dimension, set the Type property of the dimension to Time. This enables Analysis Services to correctly use dedicated Multidimensional Expressions (MDX) time functions. Also, client applications take advantage of this knowledge to provide additional intelligence and an improved user experience.
It is also important to set attribute types so that they are compatible with a time dimension. Correctly setting the attribute types enables Analysis Services to use time-related MDX functions on the dimension, and enables the Business Intelligence Wizard to apply time intelligence to the dimension.