There can be only one date/date-time dimension in the eazyBI “Issues” cube, and there is already a “Time” dimension with that data type out-of-box.
Instead of importing your date picker Jira field as a separate dimension, it should be enough to import it as a measure and property. Then use the numerical measure "Issues with " with the “Time” dimension members.
When using the “Time” dimension with that numerical measure, eazyBI would count the issues where your date picker field value belongs to the selected/displayed period.
This approach gives an option to analyze different events on one timeline.