Defining a Date Dimension creates an implicit hierarchy among the different levels available: years, quarters, months, weeks and days. This makes the definition easier.
Given the importance of this dimension type and the frequency of its use in models, O3 Designer includes this separate dimension for the creation of date dimensions. O3 Designer extracts each of the hierarchy levels from a Date field for the user rather than requiring that the Designer do this.
You can also define relative dates within a date dimensions. This functionality allows you to group information for certain time periods in date dimensions. They are especially useful for time analysis, where the standard date dimension may not be enough
Users can also define the label that should be shown in the case of Null dates, as well as the format used to display dates in general.