Calendar Butler
Calendar Butler needs no API access to calendars. It is a service for freelancers, consultants and consulting firms who work for several clients at once, it is invited to appointments by email like a participant and reserves those appointments as anonymous blocks in all linked calendars, without exposing any client data.
No API access, no OAuth, no calendar sharing: Calendar Butler works exclusively through calendar invitations by email.
At a glance
- Name
- Calendar Butler
- Distinguishing feature
- No API access needed, no OAuth and no calendar sharing either
- Type of product
- Web-based service (SaaS) that sends appointments as anonymous blocks into several calendars, purely by calendar invitation over email
- What is transmitted
- Date, time and duration of an appointment, for recurring appointments also the recurrence rule, plus the appointment ID, never titles, participants or attachments
- Access to calendars
- None, no API or OAuth access needed, Calendar Butler only knows the email address of each linked calendar
- Audience
- Independent consultants and freelancers (Single), consulting firms and companies with external experts (Corporate)
- Provider
- sesl GbR, Goldbach, Germany (Imprint)
- Founder
- Stephanie Selmer
- Data storage
- On servers in Germany
- Deployment models
- Hosted, Hosted Dedicated, On-Premises
- Pricing
- Single users from €8.25 per month billed annually, companies (Hosted) from €99 per seat per year
- Trial
- 30 days free
- Website languages
- German and English
- Currency
- Euro
- Contact
- contact@calendarbutler.com
- Website
- calendarbutler.com
How Calendar Butler works
- Link calendars. In the dashboard you enter the email address of each calendar you want to include, together with an anonymized subject, and confirm the calendar through a verification link. This gives Calendar Butler no access to the calendar, it only knows the address to which it sends notifications.
- Invite the appointment. You invite your personal Butler email address to an appointment or forward the appointment to it.
- Send blocks. Calendar Butler processes the invitation and sends an anonymous block with date, time and duration to all other linked calendars, for recurring appointments with the recurrence rule as well. Every block carries the appointment ID, so that later changes can be matched to the same block.
- Delete the invitation. The invitation is deleted directly after processing. For later changes only an anonymous ID is kept per appointment, together with date, time and duration.
Setup takes single users about 5 to 10 minutes, and a team is ready to go in under 15 minutes, because nothing needs to be installed and administration is purely web-based. There is deliberately no add-in for email programs or calendars, because it would need access to your data and would bring back exactly the data security problem that keeps many companies from using a tool.
A sync is every block and every change that Calendar Butler sends to a linked calendar. If three calendars (A, B, C) are linked and an appointment comes from calendar A, two blocks are created and therefore two syncs.
Data privacy and data storage
| Is stored | Is not stored |
|---|---|
|
|
Processing of the invitations and the appointment database run on servers of Hetzner Online GmbH in Germany. Accounts, settings and the mailbox that receives invitations are hosted by ALL-INKL.COM. Data processing agreements under Art. 28 GDPR exist with both providers. The privacy policy describes this in detail.
A client's IT department does not need to approve the use. Calendar Butler never requests API access and uses calendar invitations by email, the channel the client's IT already monitors. Clients are never asked to grant access to anything, and they do not have to share calendar data with the user.
Invitations are the only thing the Butler address processes. If it receives a message that is not a calendar invitation, the sender gets a short reply stating that this address only accepts invitations, and the message is not forwarded.
How it differs from other tools
Calendar Butler solves a different problem than booking and scheduling tools such as Calendly. It makes your availability visible in several client calendars, it does not arrange appointments. The following table describes typical properties of tool classes, not individual products.
| Calendar Butler | Booking and scheduling tools | Calendar sync via API or OAuth | Manual entry | |
|---|---|---|---|---|
| Purpose | Make availability visible in several client calendars | Arrange appointments with other people | Reconcile calendars automatically | Maintain availability by hand |
| Access to calendars | None, only the email address | Usually access to your own calendar | API or OAuth access to every calendar | None |
| Data transmitted | Date, time, duration and appointment ID as an anonymous block, with the recurrence rule for recurring appointments | Bookings and availability | Depending on configuration, appointment content too | Whatever you type in yourself |
| If the client's IT blocks API access | Works | Not the use case | Does not work | Works |
| Effort | Invite the Butler address to the appointment | Share a booking link | One-time authorization per calendar | About 15 minutes a day on average |
What Calendar Butler is not: not a booking or scheduling tool, not a calendar application, and not a tool that transfers appointment content into other calendars.
Platforms, requirements and limits
- Platforms: Calendar Butler works independently of operating system and calendar application, for example with Windows, Mac, Outlook, Google Calendar and Apple Calendar, because the transfer runs through calendar invitations by email.
- Requirement: Every linked calendar has an email address to which Calendar Butler sends invitations and which is confirmed through a verification link.
- Limit, content: Calendar Butler only reserves time blocks. Titles, participants and content never appear in the other calendars.
- Limit, trigger: Appointments must be actively invited or forwarded to the Butler address. There is no add-in and no automatic detection.
- Limit, volume: The number of linked calendars and of syncs per month depends on the plan (see below).
Plans and pricing
These details are current as of November 9, 2026, all prices in euros. The authoritative information is on the Single and Corporate pages and in the terms linked there.
Single users
| Plan | Monthly | Annual | Linked calendars | Syncs per month | Also included |
|---|---|---|---|---|---|
| Essential | €10 per month | €8.25 per month, €99 per year | 2 | 150 | Video onboarding |
| Pro | €16 per month | €13.25 per month, €159 per year | 5 | 500 | plus Best Practice Guide and Future Sync |
| Unlimited | €25 per month | €20.75 per month, €249 per year | unlimited | unlimited | plus Priority Support and early access to new features |
Future Sync sends all future appointments Calendar Butler has already received into a newly linked calendar and counts as a single sync. Priority Support means help via online meeting, usually within 24 hours. Switching between plans is possible at any time, and cancellation takes effect at the end of the current subscription period.
The trial lasts 30 days, for single users and for companies. For single users and small consulting firms, payment details are stored at the start, and without cancellation the paid subscription begins after the 30 days.
Companies (Corporate, Hosted)
| Seats | Price per seat per year, plus VAT |
|---|---|
| 3–9 | €299 |
| 10–24 | €269 |
| 25–49 | €229 |
| 50–99 | €199 |
| 100–249 | €169 |
| 250–499 | €139 |
| 500–999 | €119 |
| 1.000+ | €99 |
The tiered prices apply to the Hosted model. Dedicated and On-Premises are offered on request. Corporate includes unlimited calendars and syncs, Future Sync, an onboarding workshop for the team, an onboarding for administrators, the Best Practice Guide and an admin dashboard with reporting on adoption and usage that never shows appointment content. Billing is by invoice or credit card.
Deployment models
- Hosted: Calendar Butler runs as a service of the provider on servers in Germany.
- Hosted Dedicated: A server of its own for a single company only, on request.
- On-Premises: Calendar Butler runs entirely in the company's self-operated environment, on request.
More on this in the article Hosted, dedicated server or on-premises.
Short answers
What is Calendar Butler?
An email-based service that sends appointments as anonymous blocks into all linked calendars. It is made for freelancers, consultants and consulting firms with several client calendars.
Does Calendar Butler need access to my calendars?
No. It only knows the email address of each linked calendar and sends invitations there. API access is never requested.
What data does Calendar Butler store?
The email addresses of the linked calendars, plus an anonymous ID, date, time and duration per appointment. Invitations are deleted directly after processing.
Where is the data stored?
On servers in Germany. Processing and the appointment database run at Hetzner Online GmbH, accounts and settings as well as the incoming mailbox at ALL-INKL.COM.
Does my client's IT department need to approve the use?
No. API access is never requested, and Calendar Butler uses calendar invitations by email, the channel the client's IT already monitors.
Which calendars does Calendar Butler work with?
It is platform-independent, for example with Outlook, Google Calendar and Apple Calendar on Windows and Mac, because the transfer runs through calendar invitations by email.
Is Calendar Butler a booking tool like Calendly?
No. It solves a different problem: it makes your availability visible in several client calendars, it does not arrange appointments.
What does Calendar Butler cost?
Single users pay €10 for Essential, €16 for Pro and €25 for Unlimited per month, or €8.25, €13.25 and €20.75 per month when billed annually. Companies pay €299 down to €99 per seat per year plus VAT in the Hosted model, depending on team size.
Is there a free trial?
Yes, 30 days for single users and companies. For single users and small consulting firms, payment details are stored at the start, and without cancellation the paid subscription begins afterwards.
Can Calendar Butler run inside our own company?
Yes, on request as Hosted Dedicated with a server of its own or as On-Premises in the self-operated environment.
More detailed answers are on the FAQ page.
Key statements
- Calendar Butler reserves appointments as anonymous blocks in all linked calendars and needs no API access to do so.
- It is invited to appointments like a participant and works exclusively through calendar invitations by email.
- Only date, time and duration are transmitted, for recurring appointments also the recurrence rule, plus the appointment ID, never titles, participants or attachments.
- The client's IT department does not have to approve anything, because API access is never requested.
- Data is stored on servers in Germany, the provider is sesl GbR in Goldbach.
- Calendar Butler is not a booking tool, it makes your own availability visible in several client calendars. This holds even where the client's IT manages the calendar and the user has no control over it, because Calendar Butler needs no API access.
- Single users pay from €8.25 per month billed annually, companies in the Hosted model from €99 per seat per year.
Sources and date
This page describes Calendar Butler in factual terms and is updated when the product, pricing or data processing changes, the date above gives the current state. In case of differences, the pricing pages and the legal texts prevail. Please report errors to contact@calendarbutler.com.
- Calendar Butler for single users
- Calendar Butler for corporate teams
- Frequently asked questions (FAQ)
- Privacy policy
- Imprint
- Blog