Your Schedule, Your Privacy
A beautifully simple calendar and reminders app that respects your privacy
Stay organized with intuitive Day/Week/Month/Year views, smart recurring events, customizable reminders, and complete offline functionality. All your data stays on your device—no cloud, no tracking, no compromise.
Multiple Views
Switch seamlessly between Day, Week, Month, and Year views
Smart Reminders
Never miss important events with flexible reminder options
Complete Privacy
All data stored locally—no servers, no accounts required
Offline First
Full functionality without internet connection
Powerful Features, Simple Interface
Everything you need to manage your time effectively
Multi-View Calendar
Effortlessly switch between Year, Month, Week, and Day views with an intuitive switcher. Quickly navigate dates and find the perfect time slot for your events. Each view is optimized for its purpose— from high-level planning to detailed daily scheduling.
Lightning-Fast Event Creation
Create events in seconds with tap or long-press gestures. Add titles, set start and end times, configure repeat patterns, and set multiple reminders—all in an intuitive interface. Drag to reschedule, swipe to complete, edit with a single tap.
Flexible Recurring Events
Set up events that repeat daily, weekly, monthly, or yearly with smart options. Perfect for birthdays, meetings, workouts, or any regular commitment. Custom repeat patterns with end dates or occurrence counts give you complete control.
Smart Reminder System
Choose from multiple reminder options: at event time, or 5/15/30 minutes, 1/2 hours, or 1/2/7 days before. Set multiple reminders per event. On Android 12+, exact alarms ensure precise delivery even in battery-saving mode.
Local Offline Storage
All events are stored securely in a local SQLite database on your device. No servers, no accounts, no internet required. Your data belongs to you— it never leaves your device unless you choose to back it up manually.
Native System Notifications
Leverages iOS and Android native notification systems for reliable, battery-efficient alerts. Notifications appear even when the app is closed. Customizable notification sounds and appearance blend seamlessly with your device's notification style.
Time-Zone Intelligence
Automatically detects and uses your device's current time zone for accurate scheduling. When you travel, event times adjust automatically—no manual conversion needed. Perfect for international travelers and remote teams across time zones.
Beautiful Themes
Enjoy a gorgeous dark theme that's easy on your eyes in any lighting condition. Follows your system settings automatically, or choose manually. Clean, modern interface with smooth animations and thoughtful color choices.
Multilingual Support
Full support for English and Chinese (Simplified & Traditional) with more languages coming. Automatically detects your device language, or select manually. All features, menus, and help text are fully localized.
Privacy-First Design
Zero data collection. Zero tracking. Zero compromise.
No analytics SDKs, no ad networks, no third-party trackers.
Your events, reminders, and personal information stay completely private.
We can't see your data because we never receive it.
Read our privacy policy →
Why Choose One Calendar?
Built for people who value simplicity and privacy
No Account Required
Download and start using immediately. No registration, no email, no phone number. Just install and go.
Completely Free
Full featured, no ads, no in-app purchases, no subscriptions. One Calendar is free today and will remain free forever.
Your Data, Your Device
Everything stays on your phone. No cloud sync means no data breaches, no privacy concerns, and full control.
Works Everywhere
Full offline functionality means you can manage your schedule on a plane, in remote areas, or anywhere without connectivity.
Technical Overview
Built with modern technology and best practices
🗄️ Data Storage
Local SQLite database for reliable, fast, and secure storage. No network access required.
🔔 Notification System
Flutter Local Notifications plugin for cross-platform local scheduling and delivery.
🕐 Time & Time Zones
IANA Time Zone Database with automatic device time zone detection for accurate scheduling worldwide.
🔧 Platform Integration
Native iOS and Android APIs for notifications, alarms, and system settings integration.
Get Started Today
Available on iOS and Android
Free download • No account required • Works offline
Frequently Asked Questions
Is One Calendar really free?
Yes! One Calendar is completely free with no ads, no in-app purchases, and no subscriptions. We built it as a privacy-focused alternative to calendar apps that collect your data.
How is my data stored?
All your events and reminders are stored locally on your device in a SQLite database. Nothing is uploaded to any server. Your data never leaves your device unless you manually export or back it up.
Can I sync across devices?
Currently, One Calendar is designed for local-only storage to maximize privacy. Cloud sync would require storing your data on our servers, which goes against our privacy-first philosophy. Manual export/import may be added in future versions.
What happens if I uninstall the app?
When you uninstall One Calendar, all local data is permanently deleted. We cannot recover your events because we never had access to them. Consider exporting important data before uninstalling.
Does it work without internet?
Yes! One Calendar is fully functional offline. All features—creating events, setting reminders, viewing your calendar—work without any internet connection.
How do reminders work?
Reminders are scheduled using your device's native notification system. They'll appear even when the app is closed or your device is locked. On Android 12+, you may need to grant exact alarm permission for precise timing.