Dimensions Dim-Date, Dim-Date Fiscal Calendar are Standard or Canonical Time Dimensions that are used to analyze almost all of the Fact metrics across subject areas. The Facts joins to these dimensions on the standard date attributes that they would be analyzed by. They can be used for performing a cross-fact analysis across modules.
For example, if a functional requirement is to analyze the Procurement metrics and compare them with the Payable or Receivable metrics, then you can use the Dim-Date or Dim-Date Fiscal Calendar to perform this cross-functional area analysis. The Time dimension attribute can be selected along with the Procurement metric and the Payable or Receivables metrics across subject areas.