[Feature Request] Set timezone for response timeline output

Currently the date tag on the timeline output defaults to GMT (which is not local time). It would be good to either have this default to local time or be configurable.

Example output in the Timeline tab of a response:
```
< HTTP/1.1 500 Internal Server Error
< Content-Type: application/json; charset=utf-8
< Server: Microsoft-IIS/10.0
< X-Powered-By: ASP.NET
< Date: Wed, 23 Oct 2019 03:33:32 GMT
< Content-Length: 43
```

Start in the Timeline tab by reproducing the response output shown in the issue and identify where its Date header timestamp is rendered. The work is done when the timeline date uses local time by default or provides a configurable timezone, with the resulting behavior verified against the example.

Written by the indexing model from the issue text.