Doc-value related warnings filling the log

Elastic Stack Elasticsearch
1

I am seeing the following warning fill the log -

Doc-value field [@timestamp] is not using a format. The output will change in 7.0 when doc value fields get formatted based on mappings by default

I am wondering which aspect of the configuration I need to modify to resolve this.

Thank youj!

2

I went into 'Index Settings' for Kibana, and switched the format of @timestamp from '-default-' to 'Date', saved and then refreshed the fields.

Hoping that was all I needed to do.