I am new to Elasticsearch. I am sending the Purelytics data from Dynatrace to ES and can see the data on Kibana. we have observed that data.startTime and data.endTime of JSON documents are mapped to Number data type. We are not able to modify the existing index data types. So, I have created the new index and modified the mappings of data.startTime and endTime to Date format, able to see that change in ES but not reflected on Kibana webpage. So could you please suggest what would be the better option to do so.