1. Set Environment Variable to UTC:

TZ=UTC temporal server start-dev --ui-port <MY_PORT_NUMBER> --db-filename myfile.db

This sets logs to UTC.

2. Use a Custom Config File: Create a config file (config.yaml) with the desired format:

log: timeFormat: "2006-01-02T15:04:05.000Z"

3. Start the server with:

temporal server start-dev --config config.yaml --ui-port <MY_PORT_NUMBER> --db-filename myfile.db

This forces UTC with precise timestamp control.