📅 Scheduling · $4.75/mo

Can I vibe code Fantastical?

Calendar app with natural-language event entry, Mac and iOS.

🟢Yes — build itest. multi-day

Fantastical doesn't own your calendar — Apple's EventKit and CalDAV do — so you're building a nicer front end, and the marquee feature is suddenly cheap: parsing 'lunch with Sam next Tuesday at 1' used to be their crown jewel, and now an LLM call or chrono-node does it in an afternoon. What keeps this multi-day is the rest of a calendar client: month and week views, recurring events, and time zones will eat the weekend. A menu-bar quick-add that writes to your real calendar captures most of the magic.

The one-shot prompt
Build a macOS menu-bar app in Swift for natural-language event entry into my real calendars. A global hotkey opens a small input window; I type 'dentist thu 2pm 45min' or 'standup every weekday 9:30'; parse it with chrono-node-style rules or a single LLM call returning {title, start, end, recurrence, calendar}, show a confirm preview, then write via EventKit. Include a today/next-7-days agenda dropdown and a settings pane for default calendar and durations. Handle time zones explicitly. Keep it a single small Xcode project with EventKit permission handling done right.
Paste into Claude Code, Codex, or your agent of choice — then steer. Learn the moves in Prompt Engineering.
What you build

A menu-bar quick-add for your Mac: type 'coffee with Ana Friday 3pm', an LLM parses it, and the event lands on your real calendar — plus a simple agenda view.

What you give up
  • Polished month, week, and year views across Mac, iPhone, iPad, and Watch
  • Calendar sets, weather, and travel time — the long tail of thoughtful features
  • Meeting proposals and scheduling links built into the client
  • A decade of recurring-event and time-zone edge cases already fixed
Why people still pay

A calendar client must be flawless every single day, and Flexibits has pre-paid the years of edge-case debugging you'd otherwise fund with missed meetings.

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Actually build it

A prompt is the first move, not the whole game. Course 01 teaches you to take a prompt like this one to a shipped, working app — reviewing, correcting, and steering the agent the whole way.

Start Course 01 →