report when date changes

Need to be able to have a report show all Initiatives where a specific date field has been changed in a given time period. Ex: If Field A has changed in the last 15 days, the initiative shows on the report with the old and new dates. If no change to that field, the initiative does not show on the report.

Use Case: We have a custom date field for committed launch date on Initiatives. If that date changes we want an easy way to identify it so we can understand implications on the larger portfolio in terms of resources, impact to customers, etc...