# How to Vibe Code Your Own Fantastical (and Stop Paying for It)

> Events. Tasks. Meetings.

- Site: https://flexibits.com
- Category: Productivity
- Platforms: macOS app, iOS app
- Verdict: **Serious undertaking** (38/100 vibecodeable)
- Estimated effort: 6+ weeks of focused native development

## Verdict

Build a simplified macOS/iOS native calendar subset using SwiftUI, but expect weeks of frustration replicating robust natural language parsing and bidirectional CalDAV sync.

Replicating Fantastical's polish requires building a native Swift app rather than a web app. The hardest engineering challenges are not the UI grids, but writing a deterministic natural language engine that parses 'Lunch with John on Tuesday at 12pm' into exact date objects, while handling credential storage in the macOS Keychain and synchronizing reliably against external CalDAV servers without dropping events.

### What you can't replicate

- The exact 15-year polish and sub-millisecond native animation fluidity of AppKit/SwiftUI components
- Pre-built enterprise integrations for dozens of proprietary conference call providers and calendar syncing layers
- Deep platform hooks like Apple Watch watchOS complications and system-level menu bar daemons

## What it does

A feature-rich calendar and task management client known for natural language text parsing, full-screen views, scheduling links, and cross-device sync.

### Core features

- Natural language text parsing for events and tasks
- Multi-view calendar (Day, Week, Month, Quarter, Year)
- CalDAV and local event synchronization
- Scheduling links ('Openings' and 'Proposals')
- Conference call link auto-detection
- Weather forecast integration and travel time calculation
- Widgets and menu bar / lock screen Live Activities

## The business

### Pricing

- Free: Free — Basic calendar and task views with local calendar connection.
- Individual: $4.75/mo — Full control of calendars, natural language parsing, and scheduling links.

Founded 2011.
Team size: 11-50 employees.

## The hard parts

- Robust natural language date/time parsing engine handling ambiguous human inputs across locales
- Bidirectional background push sync with fragmented external CalDAV, Exchange, and Google APIs
- Native macOS and iOS performance with complex custom UI components (DayTicker, calendar grid views)
- Secure local credential management via Apple Keychain and encrypted end-to-end sync metadata

## How to vibe code Fantastical

### Prerequisites

- Apple Mac: Required to compile and run native macOS and iOS applications using Xcode.
- Xcode (Free): The official IDE for building native Swift and SwiftUI applications.
- Node.js (Free): Required for running auxiliary tooling and local backend services if building a custom sync server.
- GitHub (Free): Source code repository hosting and version control during development.

### Recommended AI tools

- Claude Code: Best-in-class terminal coding agent for scaffolding multi-file Swift projects and debugging complex state management loops.
- Cursor: AI-native code editor ideal for fine-tuning SwiftUI layout hierarchies and managing swift package dependencies.

### Stack

- Frontend: Swift & SwiftUI (Native macOS/iOS)
- Backend: TypeScript on Cloudflare Workers
- Database: Turso (SQLite at the edge)
- Auth: better-auth
- Payments: Stripe
- Other: EventKit framework for local calendar access, Anthropic API for natural language event parsing

### Hosting

- Cloudflare (Hosts the lightweight backend API handling scheduling links, webhooks, and account metadata sync.): $0-5/mo

### Build guide

1. **Initialize Native Swift Project & EventKit Integration** — Create a new multiplatform SwiftUI app targeting macOS and iOS. Request permissions for EventKit and build the local calendar data provider wrapper to fetch existing calendars and events.

```
Create a new SwiftUI multiplatform app structure for macOS and iOS. Implement an EventKit manager class in Swift that requests calendar access permissions from the user, queries system calendars, and retrieves events for a given date range. Write unit tests to verify event fetching and error handling when permissions are denied.
```

2. **Build the Natural Language Parsing Engine** — Implement a natural language input parser that extracts event titles, start times, end times, and recurrence rules from raw text strings using structured LLM prompts or regex parsing.

```
Build a Swift utility service that takes a raw natural language string (e.g., 'Lunch with Sarah on Tuesday at 12pm for 1 hour') and calls an LLM endpoint or uses regex extraction to return a structured ParsedEvent struct containing title, startDate, endDate, location, and attendees. Handle edge cases like missing times or ambiguous dates gracefully.
```

3. **Design the Calendar Grid and DayTicker UI** — Create a custom SwiftUI calendar interface supporting day, week, and month views, complete with a horizontal DayTicker component for quick date navigation.

```
Design and implement a SwiftUI custom calendar view featuring a horizontal scrolling DayTicker at the top, a multi-day grid for the week view, and a full-month grid layout. Ensure smooth scrolling performance, support tap-to-select day interactions, and render events dynamically based on the selected date interval.
```

4. **Implement Cloudflare Worker Backend for Scheduling Links** — Set up a TypeScript backend on Cloudflare Workers backed by Turso SQLite to handle public scheduling pages ('Openings') and booking requests.

```
Create a Cloudflare Worker backend using TypeScript and Turso for database storage. Implement API routes to create scheduling rules ('Openings'), check availability slots against busy intervals, and accept booking requests from external invitees. Include input validation and JSON response schemas.
```

5. **Add Conference Call Detection & Menu Bar Quick Access** — Implement conference link detection (Zoom, Google Meet, Teams) to display one-click join buttons, and add a native macOS menu bar status item.

```
Implement a Swift service that scans event notes and locations for conference call URLs matching Zoom, Google Meet, Microsoft Teams, and FaceTime. For macOS, add a MenuBarExtra status item that displays the next upcoming meeting with a single-click 'Join' button that launches the detected URL.
```

### Cost vs paying

**Starting costs (one-time):**

- Apple Developer Program Membership (if distributing to devices): $99/yr
- AI Coding Assistant subscription (Claude Pro / Cursor): $20
- Total: ~$119 one-time

**Ongoing costs (monthly):**

- Cloudflare Workers & Turso Database: $0/mo (Free tier)
- Total: $0/mo

- Paying for the SaaS instead: $4.75/mo
- Build time: 60-80 hours
- AI tool credits: $20
- Break-even: 25 months (primarily a learning project)

## Sources

- [Flexibits Official Website](https://flexibits.com)
- [Flexibits Privacy FAQ & Architecture Details](https://flexibits.com/privacy)
- [Flexibits Pricing Overview](https://flexibits.com/pricing)