Self-Hosted Alternatives to Outlook Calendar
Why Replace Outlook Calendar?
Outlook Calendar comes bundled with Microsoft 365, which costs $6.99-12.99/month per user. For personal use, that’s $84-156/year for a calendar — expensive when free, open-source alternatives exist. Beyond cost:
- Data ownership: Microsoft stores and processes your calendar data, including event titles, attendee lists, and locations. They use this data for “productivity insights” and AI features.
- Vendor lock-in: Migrating away from Microsoft 365 is painful. Calendar data is the easy part — breaking the ecosystem dependency is hard.
- Subscription fatigue: You pay monthly forever. Self-hosted CalDAV servers run on hardware you already own.
- Privacy: Meeting titles and attendee lists are business-sensitive data. Self-hosting keeps it on your infrastructure.
CalDAV is the open standard that every calendar app supports. Replacing Outlook Calendar means switching to CalDAV — any compatible client (Thunderbird, iOS Calendar, Android DAVx⁵) works seamlessly.
Best Alternatives
Radicale — Best Lightweight Replacement
Radicale is a minimal CalDAV/CardDAV server that runs in 15 MB of RAM. File-based storage — no database needed. Zero configuration for basic use. Deploy in under 5 minutes.
For a personal Outlook Calendar replacement, Radicale is the simplest path: install, create a user, add the account on your devices.
[Read our full guide: How to Self-Host Radicale]
Baikal — Best for Teams and Families
Baikal adds a web admin panel for managing users, calendars, and address books. Uses SQLite or MySQL. The best choice when you need to manage multiple users without CLI access — click to create accounts, set permissions, and configure calendars.
If you’re replacing Outlook Calendar for a small team or household, Baikal’s admin UI saves time over Radicale’s file-based management.
[Read our full guide: How to Self-Host Baikal]
Davis — Best CalDAV/CardDAV + WebDAV Combo
Davis combines CalDAV, CardDAV, and WebDAV (file sharing) in one server. Built on sabre/dav, the same CalDAV library that powers Nextcloud’s calendar. If you want calendar + contacts + basic file sharing without running Nextcloud, Davis consolidates three services into one.
[Read our full guide: How to Self-Host Davis]
Migration Guide
Export from Outlook
Outlook Desktop (Windows):
- File → Open & Export → Import/Export
- Select “Export to a file” → Next
- Choose “Comma Separated Values” or “Outlook Data File (.pst)” → Next
- Select your calendar folder → Next
- Choose save location → Finish
Outlook Web (Microsoft 365):
- Go to calendar.live.com or outlook.office.com
- Settings (gear icon) → View all Outlook settings
- Calendar → Shared calendars
- Under “Publish a calendar,” select your calendar and “Can view all details”
- Copy the ICS link and download the
.icsfile
Thunderbird (if you sync Outlook via IMAP):
- Right-click your calendar → Export Calendar
- Save as
.icsfile
Import to CalDAV Server
# Import to Radicale
curl -T calendar.ics -u username:password \
https://cal.example.com/username/default/
# Import to Baikal — use Thunderbird or DAVx⁵ to import the .ics file
# Baikal doesn't have a CLI import tool
# Import to Davis — similar to Baikal, use a CalDAV clientClient Setup
Thunderbird: Account Settings → Calendar → New Calendar → On the Network → CalDAV → Enter your server URL and credentials.
iOS: Settings → Calendar → Accounts → Add Account → Other → Add CalDAV Account → Enter server, username, password.
Android: Install DAVx⁵ from F-Droid or Play Store → Add account → Enter base URL and credentials → DAVx⁵ auto-discovers calendars.
Windows Mail/Calendar: The built-in Windows app supports CalDAV via “Other Account” → “Internet Calendar.” However, the experience is limited. Use Thunderbird for the best desktop CalDAV client on Windows.
Cost Comparison
| Outlook Calendar | Self-Hosted CalDAV | |
|---|---|---|
| Monthly cost (personal) | $6.99 (Microsoft 365 Personal) | $0 (runs on existing server) |
| Monthly cost (family/team) | $9.99 (Family) or $12.99 (Business) | $0 |
| Annual cost | $84-156/year | $0 additional |
| 3-year cost | $252-468 | $0 |
| Users included | 1-6 (Family plan) | Unlimited |
| Calendar sharing | Yes (within Microsoft ecosystem) | Yes (standard CalDAV) |
| Cross-platform | Good (iOS/Android apps available) | Excellent (CalDAV is universal) |
| Privacy | Microsoft processes data | Full control |
| Offline access | Via Outlook apps | Via CalDAV clients |
What You Give Up
- Outlook integration: If you use Outlook for email, losing the integrated calendar is a real downgrade. Consider whether you need to keep Outlook for email while using CalDAV for calendaring.
- Microsoft Teams meeting scheduling: Creating Teams meetings directly from calendar invites won’t work. You’d need to create meetings separately.
- Scheduling assistant: Outlook’s free/busy lookup for colleagues requires Exchange/Microsoft 365. CalDAV has free/busy support but it only works between CalDAV users.
- Outlook mobile app: The Outlook app is polished. Replacing it with DAVx⁵ + Google Calendar (or another CalDAV-compatible app) works but isn’t as seamless.
- AI features: Microsoft Copilot calendar features (meeting summaries, scheduling suggestions) are tied to Outlook.
For personal calendar use, the switch is easy and the trade-offs are minimal. For enterprise Outlook users with heavy Teams and Exchange integration, self-hosted CalDAV replaces the calendar but not the ecosystem.
Frequently Asked Questions
Can I sync a self-hosted calendar with my iPhone and Android phone?
Yes. iOS has built-in CalDAV support — add your server under Settings → Calendar → Accounts → Add Account → Other → CalDAV. On Android, install DAVx⁵ (free on F-Droid, $5 on Play Store) to sync CalDAV calendars with the built-in calendar app. Both platforms sync bidirectionally — create events on your phone or desktop and they appear everywhere.
Can I share calendars with other people?
Yes. CalDAV supports shared calendars natively. In Baikal and Davis, create multiple calendars and assign access to different users through the admin panel. Radicale supports sharing via URL — share a read-only or read-write calendar link. CalDAV clients like Thunderbird and DAVx⁵ handle shared calendar subscriptions. You won’t get Outlook’s scheduling assistant (free/busy lookup) unless all participants use CalDAV.
Do self-hosted CalDAV servers support recurring events and reminders?
Yes. CalDAV is a mature standard — recurring events, reminders, all-day events, time zones, attendee invitations (iTIP), and event categories all work. Your CalDAV client handles the UI; the server stores and syncs the data. The experience is identical to Outlook Calendar for standard calendar features.
How much server resources does a CalDAV server need?
Minimal. Radicale uses 15 MB of RAM — the lightest option. Baikal uses about 50 MB with SQLite. Davis uses ~100 MB with PostgreSQL. All three run comfortably on a Raspberry Pi, an old laptop, or the smallest VPS tier. A CalDAV server handling 10 users with thousands of events uses fewer resources than most web applications.
Can I import my existing Outlook calendar into a self-hosted CalDAV server?
Yes. Export your Outlook calendar as an ICS file (File → Open & Export → Import/Export in desktop Outlook, or through Outlook Web settings). Import the ICS file into your CalDAV server — Thunderbird can import ICS directly into a CalDAV calendar, or use curl to upload the file to Radicale. All events, recurring patterns, and reminders transfer via the standard ICS format.
Will I lose meeting invitations from Outlook users?
CalDAV supports email-based meeting invitations (iTIP/iMIP). When someone sends you a calendar invite by email, your email client (Thunderbird) can add it to your CalDAV calendar. However, you won’t see free/busy information for Outlook/Exchange users, and accepting invites requires email processing rather than Outlook’s one-click accept. For teams where everyone uses Outlook, this is the biggest friction point.
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