CycleOne

Overview

CycleOne is a high-performance, open-source period tracker designed for users who value privacy above all else.

In an era of cloud-connected health apps, CycleOne takes a stand: Your health data is yours alone. Built with a strict "local-only" architecture, it provides professional-grade cycle prediction, symptom tracking, and historical analysis without ever requesting network access, requiring an account, or charging a subscription fee.

Advanced Prediction Engine

Period Projection: Intelligent estimations for start dates and duration based on historical averages. Ovulation Tracking: Automatic calculation of ovulation and fertile windows. Irregularity Alerts: Identifies significant cycle variances to help you remain aware of physiological shifts.

Holistic Logging

Flow Intensity: Categorical tracking from spotting to heavy flow. Symptom Database: Track physical, emotional, and digestive indicators. Mood & Energy: Document biometric indicators with a streamlined, premium UI. Notes: Local-only annotations for detailed record-keeping.

Premium User Experience

Native Calendar: Leveraging UICalendarView for a high-contrast, interactive experience. Dynamic Themes: 5 custom accent color themes (Rose, Lavender, Ocean, Sage, Sunset) to match your style. Smooth Animations: High-fidelity transitions and staggered animations for a premium app feel. Zero Emojis: A consistent, professional aesthetic using high-quality SF Symbols.

Localization

In-app language switcher in Settings with runtime locale updates. Supported languages: English (en), Filipino/Tagalog (fil), Japanese (ja). Coverage guardrails: localization parity and source-key coverage tests in CycleOneTests/LocalizationCoverageTests.swift. Localized custom pages: Privacy Policy HTML is shipped per language resource bundle. Organized resources: language folders are grouped under CycleOne/LocalizationResources/ in source. Legend correctness: Calendar legend labels resolve localized values (not raw string keys). Round-trip stability: UI tests validate language switching Japanese -> English and verify localized legend text remains correct.

Note on folder structure:

Source files are grouped in CycleOne/LocalizationResources for maintainability while preserving runtime localization behavior.

The Privacy Manifesto

CycleOne was built from the ground up to be safe:

No Cloud Sync: Your data never leaves your device. No Accounts: No email, no password, no login required. No Analytics: Zero third-party tracking or telemetry. No Network Entitlements: The app doesn't even ask for internet permissions. Data Sovereignty: Export your entire history to CSV anytime.