Calendar Butler
1
Transfer manually
Every new appointment, every reschedule and every cancellation entered by hand into every other calendar. And let's be honest: who became a consultant for a thankless task like this?
✕Costs time and invites mistakes
Your expertise speaks for itself. Calendar Butler handles reliability.
Keep all your calendars in sync. Without API access.
You invite Calendar Butler to your meetings like a participant, and it turns them into anonymous blocks. It never reads names, titles or attachments.
- No API access needed
- No client data
- Live in under 15 minutes
Client A
9:0010:0011:0012:00
Steering committee10:00 – 11:30NamesE-mailDocs
Calendar ButlerClient B
9:0010:0011:0012:00
10:00 – 11:30Blocked
Private calendar
9:0010:0011:0012:00
10:00 – 11:30Blocked
The problem
Three ways to sync calendars. All three are blocked.
Every professional with several clients knows this.
2
Use a sync tool
The tool needs API access to your calendars, and your clients' IT does not allow that.
✕Not allowed
3
Forward externally
Forwarding the invitation would expose every connection you have into the company, and participants' names or confidential attachments would end up in a competitor's environment.
✕Exposes data
Calendar Butler is the fourth way.
How it works
It couldn't be easier.
The entire sync runs exclusively through email: simple, robust, and without you having to worry about anything.
STEP 1
The invite comes in
You simply forward the invitation to your Calendar Butler as usual, or add it directly as a participant.
STEP 2
It reduces it to a block
It only reads out what it actually needs to reliably sync the event, and creates a completely new invitation from that. The original invitation is deleted immediately.
STEP 3
It syncs everywhere
The new invitation automatically goes out to all your linked calendars, for a single event or a recurring one. Reschedules and cancellations are taken care of independently.
What comes in
Your invitation
- Time
- Date
- Names
- Email addresses
- Event titles
- Attachments
Calendar Butler never reads or processes names, email addresses, event titles, or attachments.
What goes out
An anonymous block
- Time
- Date
Nothing else ends up in your other calendars.
Takes care of data protection and IT compliance for you
Simply reserves your appointments in all your calendars
Needs no API access or other critical interfaces
Keeps your and your clients' data always secure
Your time is money
Your time is too valuable for this.
Do you actually know how expensive this annoying, pointless task really is? Most consultants block around 15 minutes every day for calendar upkeep. That adds up:
- 15 minevery day
- 1.25 ha week
- 5 ha month
- 55 ha working year
That's well more than
a full working week spent
copying calendar entries
from A to B.
At an hourly rate of those 55 hours cost you
€6,600 a yearevery year. But your time is definitely too valuable for that.
Hire your Calendar Butler now!Where our clients work
Trusted where compliance matters most
Calendar Butler is designed specifically for the collaboration between large companies and external professionals. Its users work for companies such as these:
What people who use Calendar Butler say
That's exactly what I needed. Shut up and take my money 😉
It's so easy. I don't have to spend ages setting that much up. You can basically start working right away.
Awesome! It solves such an annoying problem, and no AI involved.
Calendar synchronization is such an annoying problem. If you hadn't invented your tool, I wouldn't know how to solve it.
Why it exists
I've been in project work for about 20 years, and I can't count how often I wished for a solution like Calendar Butler. There was no other way: I simply had to build it myself!Stephanie Selmer, Organizational Developer
From the blog
Calendar chaos? It can be fixed.
November 28, 2026
Hosted, dedicated server or on-premises: When each deployment option makes sense
Hosted, dedicated or on-premises: the three deployment options of Calendar Butler explained, ordered by freelancers and medium-sized and large consulting firms.
Read more →
November 12, 2026
Data minimization as a principle: Why an anonymous block is enough
What is never stored cannot leak. Why start and end are enough for your other calendars and why an anonymous block protects more than any calendar share.
Read more →
November 5, 2026
Use case: interim manager with two mandates
Two mandates in parallel, two clients who rely on your availability, and neither may learn about the other. A typical day with the Calendar Butler.
Read more →
October 29, 2026
Your calendar is your delivery promise
A double booking costs your client time and trust, not just your nerves. Why your calendar is a delivery promise and what makes that promise reliable.
Read more →
October 27, 2026
What an ICS file contains, and which data you hand over with every invitation
Behind every calendar invitation sits an ICS file with far more data than the appointment shows. What it contains and why a block is enough for your other calendars.
Read more →
October 22, 2026
Why corporate IT is right to be stingy with API access to its calendars
Anyone who asks for API access to a corporate calendar asks for more than they need. Why IT is right to say no, and what is enough for availability.
Read more →
October 20, 2026
The best time management method is a calendar you don’t have to maintain
Eisenhower, Pomodoro, ALPEN: every time management method assumes a calendar that is correct. Why maintaining it by hand is no longer normal with several clients.
Read more →Your next step
The only decision left
Now all that's left is one decision: use the Calendar Butler as a single user, or in the Corporate version for your consulting business.
FAQ
Frequently asked questions
Questions about working with the Calendar Butler
Why should I use Calendar Butler instead of Calendly or a similar tool?
Calendar Butler solves a completely different problem than Calendly does. Calendar Butler is the right choice if you want to quickly and easily make your availability visible in various (customer) calendars.
On which platforms and with which tools does Calendar Butler work?
It doesn't matter whether you work on a Windows computer or a Mac, with Outlook, Google Calendar, Apple Calendar… Calendar Butler works reliably with all platforms.
Is working with Calendar Butler easy or secure?
Why choose between the two? We want both! Magic Link instead of passwords, 2FA, anonymization/data deletion, regular security updates and test automation, custom subject lines, calendar verification — not only make it easy for you, but also particularly secure.
Questions about setting up the Calendar Butler
How long does it take before I can start using Calendar Butler?
About 5–10 minutes, then you can start working with it right away: you'll receive your personal access link immediately after completing your subscription. Then verify your calendar mailboxes with a single click and you're ready to go.
How can I link my client calendars?
It's really easy: just enter the email address you use for your client in the Calendar Butler dashboard. With a single click, you can send a verification link to that email address. As soon as you click on it, your calendar is linked and synced with Calendar Butler.
Questions about Calendar Butler Features
What is a linked calendar?
In Calendar Butler, you can add your various calendars. Calendar Butler does not have access to these calendars; it only knows the email address and is instructed to send a notification there.
What is a sync?
A sync is the process by which Calendar Butler sends a block or a change to a linked calendar. Example: if you have linked three calendars (A, B, C) and send an event from calendar A to Calendar Butler, it creates and sends two blocks — two syncs.
What is Future Sync (available Q2/26)?
Future Sync lets you send all future appointments Calendar Butler has already delivered to you into a completely new calendar — especially useful when you acquire a new client. Future Sync counts as a single sync, regardless of how many appointments you sync.
What is a Video Onboarding?
To get started with Calendar Butler right away, you'll receive an onboarding tutorial that helps you set everything up in just a few minutes.
What is the Best Practice Guide?
In the Best Practice Guide, you'll get tips and tricks from people who have been using Calendar Butler for a while, so you don't end up saying later "if only I'd thought of that…"
What is Priority Support?
Priority Support assists you via online meeting, usually within 24 hours.
Questions about data privacy
Will my sensitive data be stored?
In order for Calendar Butler to support you, we only need your email addresses linked to your calendars. In addition, an anonymous ID is stored for each meeting so it can be changed later. That's all.
Do I have to share my customer's data?
We only need the email and calendar address you received from your customer, likely structured similarly to LASTNAME.EXTERNAL@CUSTOMER.COM. That is all we require.
What happens to the invitations Calendar Butler has received?
Invitations are deleted immediately after processing. Only individual anonymized information is retained so you can update your appointments later — a unique ID, date, time and duration.
Does my client's IT department need to activate my use of Calendar Butler?
No. Calendar Butler uses the same channel your client's IT department already monitors: calendar invitations via email. Even though Calendar Butler deletes all unnecessary data, always practice data minimization to protect your clients' internal information.