OpenNTP

OpenNTP ships a single Docker container that runs Chrony (NTP) and a Next.js UI. Every API response is NTP-backed with a fallback to Google NTP if the local Chrony server is unavailable.

What is included

• Chrony configuration in chrony/
• Next.js UI with multi-timezone digital clocks
• NTP-backed REST APIs and Swagger docs

Quick start (single container)

Build and run the OpenNTP service:

docker compose up -d --build

Default ports:

• UDP/123 for NTP
• HTTP/3000 for the UI and APIs

Set up your own NTP server

OpenNTP uses Chrony inside the container. To make it your own:

1. Edit the upstream sources and access rules in chrony/chrony.conf.
2. If you want a private server, remove the UDP/123 mapping or restrict it with a firewall.
3. Start the stack with docker compose up -d --build.
4. Point your clients to your host on UDP/123.

Example client check:

ntpdate -q <your-server-ip>

Configuration

Frontend (UI only):

NEXT_PUBLIC_NTP_EXPOSED=true|false
NEXT_PUBLIC_NTP_HOST=ntp.example.com
NEXT_PUBLIC_TIMEZONES=Bangladesh|Asia/Dhaka, New York|America/New_York

NTP sources:

NTP_SERVER_HOST=127.0.0.1
NTP_FALLBACK_HOST=time.google.com
NTP_TIMEOUT_MS=2500

The UI flags only change the display. Exposure is still controlled by Docker Compose and your firewall rules.

API endpoints

• GET /api/time - NTP-backed time payload
• GET /api/timezones - every Moment timezone with NTP time
• GET /api/health - uptime, Chrony tracking, NTP metadata
• GET /api/openapi - OpenAPI spec
• GET /docs - Swagger UI

Example response for GET /api/time:

{
	"nowIso": "2026-02-08T18:04:01.528Z",
	"unix": 1770573841,
	"timezone": "America/New_York",
	"offsetMinutes": -300,
	"source": "ntp",
	"ntp": {
		"host": "127.0.0.1",
		"source": "local",
		"warning": null
	}
}

Local UI dev

pnpm install
pnpm run dev

Open http://localhost:3000.