Our Methodology
How we ensure every calculator on Arithmora delivers accurate, trustworthy results you can rely on.
Core Principles
Accuracy First
Every formula is derived from authoritative sources — ISO standards, IANA timezone databases, and peer-reviewed mathematical references.
Transparency
We show our work. Each tool explains the formula used, any assumptions made, and the edge cases we handle differently.
Client-Side Privacy
All calculations run in your browser. Your inputs never leave your device — we cannot see what you calculate.
No Dark Patterns
No account walls, no hidden ads, no premium upsells for basic functionality. Every tool is fully free.
Formula Verification Process
Research authoritative sources for the mathematical formula (e.g., ISO 8601 for date arithmetic, IANA tz database for timezone rules).
Implement the formula using battle-tested libraries (date-fns for dates, native Intl API for timezones) rather than custom arithmetic where possible.
Test against known reference values — e.g., verifying that Feb 29, 2024 is correctly identified as a leap day, or that DST transitions are handled on the exact correct dates.
Validate edge cases: negative inputs, extremely large values, timezone boundary transitions, midnight crossings, and year-end wraparounds.
Cross-reference results against at least two independent sources (government data, established reference sites) before publishing.
Data Sources & References
| Category | Primary Sources |
|---|---|
| Time Conversions | SI base unit definitions (BIPM), date-fns library documentation |
| Timezone Data | IANA Time Zone Database (tzdata), US Naval Observatory |
| Date Arithmetic | ISO 8601, Gregorian calendar rules, national holiday databases |
| Financial Formulas | US Bureau of Labor Statistics (salary data), IRS standards (work hours) |
Quality Standards
- All tools pass automated unit tests covering normal cases, boundary conditions, and known-tricky inputs.
- TypeScript strict mode enforces type safety across all calculator logic — preventing silent numeric errors.
- Accessibility: Every tool supports keyboard navigation, screen readers (ARIA labels), and meets WCAG 2.1 AA standards.
- Performance: Tools load in under 2 seconds on 3G connections. All calculator logic runs client-side with zero network requests.
- Mobile-first responsive design ensures usability on all screen sizes from 320px to 4K.
Editorial Responsibility
The Arithmora editorial team combines expertise in mathematics, software engineering, and user experience design. Each tool goes through a multi-stage review process: technical implementation review, formula accuracy verification, UX testing with real users, and SEO quality assurance. We regularly audit existing tools for accuracy and update them when standards change (e.g., DST rule updates, new timezone designations, or revised statistical data).
Corrections & Feedback
If you find an inaccuracy in any of our tools, please contact us. We take accuracy reports seriously and aim to verify and fix any confirmed errors within 48 hours. All corrections are noted in the tool's last-updated timestamp.