Calendar synchronisation – How to reduce appointment scheduling emails to zero

In June 2023, I was sitting at my desk with three different client computers in front of me, trying to schedule an appointment with a new client. I opened the following one after the other:

My Outlook calendar on Client A’s computer.
Client B’s Google Calendar.
Client C’s Exchange calendar via virtual desktop.
My private Apple calendar.

Then I tried to mentally juggle which time slot was free in ALL four calendars at the same time.

Five emails later, I had the appointment. And a double booking that I had to embarrassingly cancel the next day.

In short: I tried everything! Timeboxing. Getting things done. Eat the Frog. But at the end of a day I always felt unproductive. And I didn’t realize, that the problem ist not any method.

Here’s the uncomfortable truth: as a freelancer, consultant, or external trainer, you work for different companies at the same time. Each has its own calendar system. None of these systems communicate with each other. And that’s exactly why you spend hours playing email ping-pong and coordinating appointments.

In this article, I’ll show you how to automatically synchronize all your project calendars AND completely automate appointment scheduling—without your clients having to learn yet another tool.

See how a CC email can solve your multi-calendar chaos:

Go to Calendar Butler

Why synchronizing calendars is so complicated for freelancers

The core problem for us freelancers: we live in multiple calendar worlds at the same time.

The multi-client calendar chaos

Imagine you are an IT consultant and work for three different companies:

Project A (automobile manufacturer): Their strictly isolated Outlook system. Only accessible on the company network or VPN.

Project B (startup): Google Workspace, which you can only access via their browser login.

Project C (medium-sized company): Exchange Server with its own webmail.

Your private calendar: Your own appointments, private commitments, other clients.

The harsh reality: These four calendars exist in completely isolated universes. They cannot communicate with each other. IT security guidelines, different systems, and data protection requirements make synchronization practically impossible.

What happens when a new customer inquires

Customer D writes to you: “Would you have time for a kick-off meeting? How does your schedule look?”

Your mental process:

Open Outlook for Customer A (start VPN, log in)
Check Google Calendar for Client B
Open Exchange for Client C
Check private calendar
Jump back and forth between all four
Think to yourself: “Tuesday at 2 p.m. – is that free for everyone?”
Type email: “I could do Tuesday at 2 p.m. or Thursday at 10 a.m.”
Cross your fingers that you haven’t made a mistake

Time required: 10-15 minutes. Per appointment request.

The double booking trap (and why it happens so often)

Now it gets really painful:

You offer the new customer “Thursday at 2 p.m.” In your mind, you were sure: the slot was free. You checked three calendars. But you forgot that a spontaneous meeting with customer B was entered, which you quickly accepted yesterday.

Thursday morning, 1:45 p.m.: You realize you have two appointments at the same time. Panic. You have to cancel one. Unprofessional. Embarrassing. Trouble with the client.

According to a survey of freelancers on platforms such as Gulp and Hays, this happens to 67% of all freelancers at least once a week.

The hidden cost factor: time is money.

Let’s do the math:

Per appointment request: 10 minutes for calendar juggling + 5 minutes for email = 15 minutes.

An average of 2 new or rescheduled appointments per day (customer calls, project meetings, ad hoc coordination).

2 appointments × 15 minutes × 21 working days = 630 minutes = 10.5 hours per month

At a freelancer’s hourly rate of $100, that’s $1,050 in lost revenue—every month. Just because you can’t sync your calendars.

And that’s just the coordination time. Double bookings, frustrated customers, and lost orders (because the competition was able to offer an appointment sooner) are not even included in this calculation.

The usual approaches (and why they don’t work for freelancers)

Before I show you the solution, let’s briefly go over what you’ve probably already tried—and why it failed.

⚡️ The master calendar and why it doesn’t work

The idea: You keep a private “master calendar” (e.g., Google Calendar) and manually enter ALL appointments from all project calendars there.

Why this fails:

You have to enter each appointment twice (once in the project calendar, once privately).
If a customer reschedules an appointment, you have to make changes in two places.
Your customer can’t see the calendar; they book an appointment in the company’s internal calendar, and you later see it as a double booking.

Time required: 30-45 minutes daily. Not scalable.

⚡️ Tools like Zapier or IFTTT and why you can’t use them

The idea: automation! Zapier connects different calendars and copies entries back and forth.

Why it fails:

Only works with public APIs (most company calendars block this for security reasons).

For most freelancing or professional projects, this is an absolute deal breaker and negates any potential benefits.

⚡️ Calendly, Doodle & Co. don’t make it any easier

Now we come to the appointment booking tools. They promise: “Customers can simply book themselves!”

But it is and remains a dilemma:

You connect the calendar tool to your Google Calendar. Great! But even if your customers and all their employees only book appointments in your tool calendar and no longer in the company’s internal calendar (which is simply unrealistic), what about:

The Outlook calendar at Customer A?
Customer B’s Exchange calendar?
Your private Apple calendar?

That’s right: the calendar tool can’t see them. So it shows “free” slots that are actually taken. Double bookings are inevitable.

And even if you somehow manage to connect all calendars (which is usually impossible with corporate systems):

Your customers have to:

Click on a link
Navigate through a third-party website
View your availability in an impersonal interface
Book the appointment there

That doesn’t feel personal. Especially for more upscale consulting projects or conservative industries, this comes across as distant. Some customers (especially older ones) never click the link. You wait. And in the end, you end up writing emails again.

The truth: Synchronizing calendars AND solving appointment scheduling—standard tools can’t do that for freelancers with a multi-client setup.

Synchronize calendars AND find appointments—finally a solution for freelancers.

Imagine this:

Your contact at Client A wants to make an appointment with you. They look at your calendar in the company environment at DeinName.extern@KundeA.com. There, they find all your truly available slots and simply book an appointment.

And Calendar Butler does the rest:

It anonymizes the appointment.
Then it sends an invitation with the subject line “Client A” to all your other calendars.
Your other clients and you yourself see a perfectly maintained calendar at every point.

That’s Calendar Butler. And it works differently from anything you’ve seen before.

The CC email principle: invisible magic for your clients

Calendar Butler is not a “tool” that your customers have to use. It is an intelligent assistant that works in the background of your normal email communication.

The genius: For you and your customer, it is nothing more than an invitation to an appointment. No third-party websites, no “Register now.”, no confusion. Just professional communication.

You don’t have to manage your calendars

How to set up your smart calendar synchronization

The setup is deliberately kept simple. You’ll be ready to go in three steps:

Step 1: Get your Calendar Butler email address

firstname.surname@calendarbutler.com
or an address of your choice.

This address will be your appointment assistant.

Step 2: Connect all your calendars

In the dashboard, you can store and verify all calendars that should be included in the appointment search.

Setup time: Approx. 10-15 minutes for all calendars together. One-time setup.

Step 3: Use CC for appointment requests – done!

From now on, it works automatically:

A new appointment is being set up?
Set Calendar Butler to CC.
The appointment is forwarded anonymously to all calendars.

No further action is required on your part.

Who benefits from automatic calendar synchronization with Calendar Butler?

Calendar Butler isn’t for everyone. Here are the use cases where it really makes sense:

✅ Freelancers & consultants with multiple clients at the same time

Your profile:

You work for 2-5 different companies at the same time
Each company has its own calendar system
You are constantly juggling between different calendars
Double bookings are your nightmare

What Calendar Butler does for you:

All calendars are automatically synchronized
Finding appointments takes seconds instead of minutes
No more double bookings
Professional appearance with all clients
No one has to ask “Is your calendar up to date?” anymore
Customer information remains secure

Particularly relevant for freelancers on platforms such as:

Gulp
Hays
Questax
Freelance.de
Malt

Ask your freelancing agency if they are already a Calendar Butler partner. That way, you can get Calendar Butler at special rates!

What Calendar Butler costs – and what you save in return

Investment: €24 per month

That equates to:

Less than 15 minutes of your freelance hourly rate
Approximately 33 cents per day
The price of lunch

What you save:

3-4 hours of coordination time per week = $300-400 at an hourly rate of $100
No double bookings = no more embarrassing cancellations
Faster response times = more jobs won
Professional impression = higher recommendation rate
More relaxed working = priceless

Return on investment: Calendar Butler pays for itself after just two days.

Special offer for platform partners:

Freelancers from Gulp, Hays, Questax, and other partner platforms receive special conditions. Ask your platform for details!

Conclusion: Calendar synchronisation has never been easier

As a freelancer with multiple clients at the same time, you face a problem that regular employees don’t have: you live in multiple calendar worlds at the same time.

The standard solutions (manual synchronization, Zapier, Calendly) don’t really solve the problem. They are either too time-consuming, don’t work with corporate calendars, or force your clients to learn new tools.

Calendar Butler takes a different approach:

Synchronizes ALL your calendars (regardless of the system)
Works invisibly in the background of your emails
Your customers don’t have to learn anything new

The result: You save 3-4 hours per month, appear highly professional, and never lose a job again because it took too long to find a date.

Ready to beat the calendar chaos?

Go to Calendar Butler

No credit card required. No automatic renewal. Just give it a try.

Frequently asked questions:

Does this also work with my client’s isolated Outlook?

Yes! Calendar Butler is invited as another participant, receives an email with the appointment, and also sends an email invitation to the other calendars.

Can my clients see the contents of my other appointments?

No! Calendar Butler anonymizes the appointments according to your specifications. For example, you could assign your client A the client number as the subject line and no one outside would understand it.

What if I have more than 4 calendars?

No problem! Calendar Butler supports an unlimited number of calendars in the system.

This article was written for freelancers, consultants, and trainers who want to finally synchronize their various project calendars and automate scheduling at the same time. Calendar Butler runs on German servers in accordance with GDPR requirements and works with all common calendar systems.