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Kalender Sync

Sync your calendars.

Simple. Secure. Automatic.

Kalender Sync connects Outlook, iCloud, Google, GMX, WEB.DE, mailbox.org, Posteo, STRATO, Disroot & kSuite in real time – one- or two-way.

Try free for 7 days

No credit card required.

Made & hosted in Germany DSGVO konform

Currently supported providers

Google Outlook Apple iCloud GMX WEB.DE mailbox.org KSuite Nextcloud soon Posteo STRATO Disroot

Let your agent set up your syncs

Connect your agents – Claude, ChatGPT or others – to your calendars through Kalender Sync and have your syncs created just by asking. On top of that, your agent becomes your assistant: it finds free time across all your calendars, creates events and helps you plan.

Claude and Claude Cowork

Open in Claude
  1. 1 Click Connect in the directory.
  2. 2 Sign in to Kalender Sync – your account is created on the way – and connect your calendars.
  3. 3 Choose per calendar: busy only, title and time, or full details, plus optional write access.

Claude Code

  1. 1 Run in your project: Terminal
    claude mcp add --transport http \
      kalender-sync https://app.kalender-sync.de/mcp
  2. 2 Start Claude Code, type /mcp, pick kalender-sync and choose Authenticate. Then sign in and grant your calendars.
Full guide for Claude →

Set up syncs & more manually

How it works

End the calendar chaos
in 3 simple steps

Sync your calendars

01

Connect calendars

Sign up and connect your calendars in a few clicks – using the familiar Google or Microsoft login. Apple, GMX & co. connect securely via an app-specific password.

02

Choose visibility & sync

You decide: one-way or two-way sync, who sees what, and whether to share your calendar with someone else.

03

Automatically in sync

From now on it runs in the background. Blocked slots appear by themselves – never worry about double bookings again.

Connect your AI agent

01

Connect your assistant

Search for Kalender Sync in Claude or ChatGPT and hit Connect. There are no keys and no side setup, and after about two minutes the connection is live.

02

Grant your calendars

Pick the calendars your assistant should know and set for each one how much of it is visible. Work, personal or side project is entirely your call.

03

Hand off the work

Just ask where you still have two hours in one piece this week. Your assistant answers across every calendar and books the event in the right one if you want. That puts you among the more than 1,000 people who have handed their scheduling over already.

Get to know Kalender Sync in 30 seconds

Connect your calendars in a few clicks, set up syncs, connect your agent and let it become your assistant that runs your calendars for you.

Kalender Sync | Sync your calendars. Connect ChatGPT & Claude.

Clicking play loads YouTube. Data will be sent to Google.

Features

All the flexibility you need to sync your calendars

One-way or two-way sync

Sync in one direction or both: per connection, decide whether a calendar is mirrored one-way or both calendars keep each other in sync (bidirectional).

GDPR-compliant & hosted in Germany

Built in Munich, made for Europe. Your data is processed in line with GDPR and hosted on servers in Germany.

GDPR compliant Made & hosted in Germany

For yourself or to share

Sync several of your own calendars with each other – or create a sharing for someone else. They get invited, add it to their calendar, and from then on everything stays in sync.

You decide what's visible

Per sync, pick whether only "busy" or full event details transfer. You can even set the label a blocked slot appears under – e.g. your own custom label. From Basic, copies also keep their event color or get one color per calendar.

What you get when your AI knows your calendar

Every calendar on one connection

Most calendar integrations hang off a single account. Here your assistant sees your whole schedule at once: Outlook, Google, Apple, GMX, WEB.DE, mailbox.org, kSuite, Posteo, STRATO and Disroot all come together in Kalender Sync. Your provider logins stay with us and are never passed on, and everything is managed in one place.

From AI to assistant

An AI without your calendar answers in general terms. With it, it plans your day, suggests times that are genuinely free, drafts the email with the meeting options and books the event itself if you ask.

Plan my Thursday. Offer Lisa three free times. Put the call on Tuesday at 10.

You decide what your assistant sees

For each calendar you choose between busy, title with time, and full details. A calendar you don't grant doesn't exist for the assistant, and attendees or attachments never leave your calendar.

And you decide what it may do

Whether it only looks or also creates events is your call, per calendar. Every action is logged with a timestamp so nothing happens unnoticed, and you can end the connection with one click. Hosted in Germany.

Use cases

For everyone who needs to stay on top of their schedule

From tax advisors and teachers to executives: anyone juggling many appointments across multiple calendars saves time and stress with Kalender Sync.

Wall of Love

Don't just take our word for it.

Our users are our best and most honest ambassadors. See why they wouldn't go back.

Felix Hehn
Felix Hehn Founder, multi-company operator
„When you run several companies you eventually lose track of which calendar holds what. KalSync has been humming in the background for months – set it up once and never double-book again. That's how it should be."
Louis Hügle
Louis Hügle Self-employed electrician
„I'm on a job site, not at a computer. When a customer calls I need to know in a glance whether I have time – now I do. Customer appointments, supply runs, family – all in one calendar."
Julius Richter
Julius Richter Software developer (employed + freelance)
„As a dev with a day job and side projects I kept getting collisions between work and freelance. KalSync separates them cleanly now – my employer only sees 'busy', my clients see their slots. Exactly how it should be."
Leonid Schmidt
Leonid Schmidt Marketing manager
„What really bugged me: colleagues could see the titles of my private appointments when I blocked time. Now it just says 'busy' – sounds small, but it makes a real difference."
Oliver Hasenzahl
Oliver Hasenzahl Lecturer & manager
„I'll be honest, I'm not a tech person. But juggling lectures, office hours and management meetings in separate calendars was a nightmare. Set it up once, it runs – that's all I need."
Luis Otterbeck
Luis Otterbeck Self-employed & agency
„Between agency work, my own projects and client meetings things get messy fast. KalSync keeps it all in sync without me lifting a finger – I see in a glance when I'm actually free. De-stressed my calendar."

About us

Why we built Kalender Sync

We, Paul Koch and Julius Hasenzahl, are both founders running multiple companies — which means we juggle a thousand calendars too. We know the double-booking pain. What we were missing: a solution that's truly GDPR-compliant, made in Europe and leaves us in control — one- or two-way, with selectable visibility. So we built one ourselves.

Happy to help if you have questions or ideas for getting your sync setup even sharper.

Why we built Kalender Sync

Clicking play loads YouTube. Data will be sent to Google.

From a customer

“We are absolutely impressed by the step-by-step setup and by getting exactly the result we wanted (including the selectable options we hadn't even thought of for the sync).”
Rainer Wagner, Eschner Immobilien
DEKRA-certified expert for real estate valuation Translated from German

Ready to fix your calendar chaos for good?

Try free for 7 days

Currently supported providers

GoogleMicrosoftApple iCloudKKSuiteGMXWEB.DEmailbox.orgiCal-Feeds