About CalendarIQ

CalendarIQ is a comprehensive calendar reference tool designed to help you quickly find date information, calculate day-of-week, explore week numbers, and discover holiday dates.

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How It Works

All calculations are performed instantly in your browser using proven mathematical algorithms. No data is sent to our servers, ensuring your privacy and providing lightning-fast results.

Accuracy & Methodology

CalendarIQ uses industry-standard algorithms:

• Day of Week: Zeller's congruence algorithm
• Week Numbers: ISO 8601 standard
• Holidays: Official US federal holiday rules
• Leap Years: Gregorian calendar rules

Supported Date Range

CalendarIQ supports dates from 1900 to 2100, covering most practical use cases for historical and future date calculations.

Privacy First

All date calculations and lookups happen entirely in your browser. We don't track, store, or transmit your date queries to any server. Your privacy is our priority.

Open Source & Free

CalendarIQ is completely free to use, with no ads, no registration, and no premium features. We believe calendar information should be accessible to everyone.