★★★★★
E2EE calendar integrated with Proton Mail. Zero-access encryption protects event titles, locations, and attendees.
- Zero-access暗号化
- Proton Mail統合
- 共有カレンダー
⚠ 無料枠は1カレンダー・20イベント
なぜ Google Calendar から離れる？
Events are intimate behavioral logs. Meeting attendees, medical visits, and trips can feed Google profiles for ads and AI—worth controlling elsewhere.
Googleの限界・リスク
- • Event content, attendees, and locations link to Google account profiling
- • Deep Meet/Gmail integration makes leaving the ecosystem harder
- • Shared calendars assume Google accounts—collaboration with others is constrained
- • Offline use and open CalDAV support are limited; third-party sync often needs Google API
選び方ガイド
全部試す必要はありません。あなたの優先順位に合わせて絞り込みましょう。
- 1 E2EE priority: Proton Calendar (best with Proton Mail)
- 2 CalDAV self-host sovereignty: Nextcloud Calendar or Radicale
- 3 E2EE sync with existing CalDAV clients: EteSync
- 4 Calendar bundled with quality IMAP mail: Fastmail Calendar (paid)
クイック比較
プライバシー・使いやすさ・機能・コスパの4軸で評価しています。
| ツール | Privacy | Ease of use | Features | Value | 総合 |
|---|---|---|---|---|---|
| Proton Calendar | ★★★★★ | ★★★★★ | ★★★★★ | ★★★★★ | 16/20 |
| Nextcloud Calendar | ★★★★★ | ★★★★★ | ★★★★★ | ★★★★★ | 18/20 |
| EteSync | ★★★★★ | ★★★★★ | ★★★★★ | ★★★★★ | 16/20 |
| Fastmail Calendar | ★★★★★ | ★★★★★ | ★★★★★ | ★★★★★ | 17/20 |
| Radicale | ★★★★★ | ★★★★★ | ★★★★★ | ★★★★★ | 14/20 |
すべての代替ツール（5）
★★★★★ OSS
CalDAV/CardDAV calendar in Nextcloud Hub—integrates files, contacts, tasks, and Talk.
- CalDAV/CardDAV標準
- Deck/Tasks連携
- 完全データ主権
⚠ サーバー運用が必要
★★★★★ OSS
Encrypted sync for CalDAV/CardDAV/Tasks—use existing calendar clients with an E2EE layer.
- E2EE同期
- Cal/Contact/Tasks
- 自己ホスト可
⚠ CalDAVクライアント設定が必要
★★★★
CalDAV calendar bundled with Fastmail—excellent UI, custom domains, paid professional email stack.
- CalDAV標準
- Fastmail Mail統合
- 優れたUI/UX
⚠ 有料のみ（無料枠なし）
★★★★★ OSS
Lightweight Python CalDAV/CardDAV server—personal and small-team self-host without Nextcloud overhead.
- 軽量・シンプル
- CalDAV/CardDAV
- Python製OSS
⚠ Web UIなし（CalDAVクライアント必須）
移行のヒント
- 1 Export from Google Calendar as .ics (Settings → Import & export)
- 2 CalDAV destinations work with iOS/macOS Calendar, Thunderbird, etc.
- 3 Rebuild shared calendar permissions—Google share links will stop working
- 4 Verify recurring events, reminders, and time zones after migration