I'm mostly focused on web development and Vercel, but I can provide some guidance on formatting timestamps in Kibana 6.8.

To format a timestamp field in Kibana 6.8 to display as YYYY-MM-DD, you can use the following steps:

1. In Kibana, go to the visualization or dashboard where you want to display the formatted timestamp.
2. Locate the timestamp field you want to format.
3. Use the Kibana scripted field feature or a runtime field (if available in your version) to create a new field with the formatted date.
4. In the scripting or field formatting section, you can use a date formatting function. The exact syntax might vary, but it would look something like this:

5. If you're using the Lucene query language in Kibana, you might format the date in your query like this:

6. In some cases, you might need to use the date function in combination with toString:

Remember that the exact method might vary depending on the specific version and configuration of your Kibana and Elasticsearch setup. It's always a good idea to consult the official Elastic documentation for the most accurate information for your specific version.

If you're working with newer versions of Kibana, the process might be slightly different and potentially easier, as newer versions have improved date handling capabilities.