Use of Chronological Key

Typically time dimension differs from all other dimensions in one way and that is,

All other dimensions doesn't care about the order of the values in it.

e.g. in region_dim the values are north, south, west and east. Here nobody wants to see whether north comes first or south comes first. i.e. no order is required here.

In the case of time dimension there needs to be a particular order for all the values present in it.

e.g. 2010 is earliest and 2004 is older. Dec-10 is earliest and jan-10 is older. i.e. the values in the time dimension needs to follow a particular sorting order. So the chronological key is the key which tells the obiee that the data is incrementing based on the chronological column.

For defining a dimension to be a Time dimension, we need to have a chronological Key.