Zero Calendar

AI-powered scheduling with natural language event creation, Google Calendar sync, invite emails, and analytics built on Next.js, Convex, and Better Auth.

Features

• Natural-language scheduling and calendar actions
• Google Calendar sync and webhook-based updates
• Invite flows with email delivery through Resend
• Calendar analytics, conflict detection, and free-time discovery
• Better Auth + Convex-backed authentication and user data
• Modern Next.js App Router UI

Stack

• Next.js 16
• React 19
• Bun
• Convex
• Better Auth
• OpenRouter AI SDK
• Resend

Quick start

1. Install dependencies

bun install

2. Create your environment file

Create .env.local and set the values your deployment needs:

BETTER_AUTH_SECRET=
SITE_URL=http://localhost:3000
NEXT_PUBLIC_SITE_URL=http://localhost:3000

NEXT_PUBLIC_CONVEX_URL=
CONVEX_URL=
CONVEX_SITE_URL=
NEXT_PUBLIC_CONVEX_SITE_URL=

GOOGLE_CLIENT_ID=
GOOGLE_CLIENT_SECRET=

OPENROUTER_API_KEY=
OPENROUTER_MODEL=x-ai/grok-4.1-fast

RESEND_API_KEY=
RESEND_FROM_EMAIL="Zero Calendar <email@here.com>"

3. Start Convex

If you need to regenerate Convex types or run the backend locally:

bunx convex dev

4. Start the app

bun dev

Open http://localhost:3000.

Environment variables

Variable	Required	Purpose
BETTER_AUTH_SECRET	Yes	Shared secret used by Better Auth and server-side Convex access control. Set the same strong random value in both your Next.js and Convex environments.
SITE_URL	Yes	Canonical server-side site URL used by auth flows.
NEXT_PUBLIC_SITE_URL	Yes	Public site URL used by the client and invitation links.
NEXT_PUBLIC_CONVEX_URL	Yes	Public Convex deployment URL for the frontend client.
CONVEX_URL	Usually	Server-side Convex URL. If omitted, server code falls back to NEXT_PUBLIC_CONVEX_URL.
CONVEX_SITE_URL	Yes	Convex site URL used by Better Auth server integration.
NEXT_PUBLIC_CONVEX_SITE_URL	Optional	Public override for CONVEX_SITE_URL when you need separate client/server values.
GOOGLE_CLIENT_ID	Yes	Google OAuth client ID for sign-in and calendar access.
GOOGLE_CLIENT_SECRET	Yes	Google OAuth client secret.
OPENROUTER_API_KEY	Yes	API key for AI-powered scheduling features.
OPENROUTER_MODEL	Optional	Override the default OpenRouter model.
RESEND_API_KEY	Yes	API key used to send invitation emails.
RESEND_FROM_EMAIL	Optional	Sender identity for invitation emails.

Deploying to Vercel

The deploy button above clones this repository into a new Vercel project. Before the app is usable, make sure you also:

1. Create or connect a Convex deployment.
2. Add the environment variables listed above in Vercel.
3. Configure Google OAuth for your deployed domain and Better Auth routes.
4. Set a real BETTER_AUTH_SECRET for production.
5. Configure Resend if you want invitation emails enabled.

License

MIT