Check out https://github.com/knockoph/blocktime-node
Blocktime Node is a web server that runs alongside #bitcoin core to display the node's #blocktime in a browser. It supports server-side HTML rendering to display the current blocktime when the web page is loaded or reloaded even if JavaScript is disabled in the browser and in addition supports server-sent events (SSE) for live updates if JavaScript is enabled.
The service is developed in go without any additional third-party libraries, making it easy to review and deploy.