CalendarOnline

CalendarOnline is a free, browser-based calendar and time resource website. With free online services you can rely on, we make it easier to organize your life, both at work and at home. No account, no installation, no subscription required — open it in any modern browser and start using it immediately.

Who We Are

CalendarOnline is an independently owned and operated website built by a small, passionate team of web developers and calendar enthusiasts based in India. What started as a side project to solve the frustration of finding reliable, ad-free holiday calendars has grown into a comprehensive resource used by people in over 100 countries.

As an independent project, CalendarOnline is built with a strong emphasis on simplicity, accuracy, and user privacy. Every feature, every holiday algorithm, and every design decision is made with the end user in mind. There is no venture capital, no corporate parent company, and no board of directors — just a commitment to building the best free calendar tool on the web.

Beyond the core team, CalendarOnline thrives on community contributions: users regularly report holiday inaccuracies, suggest new countries, and provide feedback that shapes the direction of the project. This collaborative approach ensures the site stays accurate and relevant across diverse cultures and regions.

Our Mission

The mission of CalendarOnline is to provide everyone in the world with free, fast, and accurate calendar and date information — regardless of their country, language, or device. We believe that something as fundamental as knowing your public holidays, calculating dates, or checking the time in another city should not require creating an account, downloading an app, or surrendering your personal data.

Our core principles:

• Free forever: CalendarOnline will always be free to use. Advertising revenue sustains the project so users never have to pay.
• Privacy first: We collect no personal data. All preferences stay on your device. We will never sell user information.
• Accuracy matters: Holiday data is computed algorithmically and continuously verified against official government sources. When users report errors, we investigate and correct them promptly.
• Universal access: The site works on any modern browser, any device, and any screen size. No installation or app store required.
• Transparency: We are upfront about how the site works, where data comes from, and how we make money (advertising only).

What We Offer

CalendarOnline provides a comprehensive suite of free calendar and date tools:

• Calendars for 100+ Countries — yearly, monthly, and daily views with accurate public holiday data
• World Clock — current time in major cities including New York, London, Tokyo, Sydney, Dubai, and more
• Date Calculator — calculate days, weeks, and months between any two dates
• Countdown Timer — count down to any upcoming date or event
• Stopwatch — precise online stopwatch for timing events and activities
• Age Calculator — exact age in years, months, and days from date of birth
• Week Number Finder — ISO week number for any date
• Printable Calendars — print any calendar view directly from your browser

Where Our Holiday & Calendar Data Comes From

Accuracy is central to CalendarOnline. Our holiday database covers public holidays, national holidays, and significant observances for over 100 countries. Rather than relying on a static, manually maintained list that quickly becomes outdated, we use a multi-layered approach to ensure data quality:

Algorithmic Computation

The majority of holiday dates are computed algorithmically each year using well-established mathematical formulas. This ensures dates are generated correctly for any year — past, present, or future. The algorithms we use include:

• Anonymous Gregorian Easter computus — computes Easter Sunday and all moveable Christian holidays (Good Friday, Ash Wednesday, Ascension Day, Whit Monday, Corpus Christi, etc.)
• Jean Meeus lunar phase equations — used for Hindu and Buddhist festivals (Diwali, Holi, Vesak, Pongal) that depend on precise lunar phase data from Astronomical Algorithms (Meeus, 1991)
• Islamic tabular calendar — calculates Islamic holidays (Eid-ul-Fitr, Eid-ul-Adha, Muharram, Milad-un-Nabi) using the standard 30-year intercalation cycle
• Japanese equinox formulas — computes Vernal Equinox Day and Autumnal Equinox Day for Japanese national holidays
• Chinese lunisolar calendar — determines Chinese New Year, Mid-Autumn Festival, Dragon Boat Festival, and Qingming Festival
• Hebrew calendar algorithms — used for Jewish holidays (Rosh Hashanah, Yom Kippur, Hanukkah, Passover)

Official Government Sources

Fixed-date holidays (Independence Day, Republic Day, National Day, etc.) and rule-based holidays (e.g., "first Monday in September") are sourced from official government gazettes, legislative acts, and national holiday proclamations. We cross-reference these annually to catch any legislative changes.

Community Verification

Users regularly report inaccuracies via our contact form. Every report is investigated and, when confirmed, corrections are applied promptly. This ongoing feedback loop from users in over 100 countries is invaluable in maintaining accuracy across diverse regional and cultural contexts.

Accuracy Limitations

Lunar-based festival dates are accurate to ±1 day of the officially declared date. Islamic holidays computed via the tabular calendar may differ from actual observance by 1–2 days due to local crescent moon sighting variations. Regional sub-national holidays (state or province level) are included for major countries but may not be exhaustive. We strongly recommend verifying critical dates with official government sources, as holiday schedules can be affected by government proclamations, regional variations, and ad-hoc declarations.

Popular Countries

• 🇺🇸 United States
• 🇬🇧 United Kingdom
• 🇮🇳 India
• 🇨🇦 Canada
• 🇦🇺 Australia
• 🇩🇪 Germany
• 🇫🇷 France
• 🇯🇵 Japan
• 🇧🇷 Brazil
• 🇨🇳 China

How It Works

CalendarOnline runs entirely in your browser. All calendar logic, holiday computation, and rendering happens locally on your device. Your preferences are stored in your browser's localStorage and are available immediately every time you open the app. No internet connection is required after the initial page load.

Technology

CalendarOnline is built with dependency-free web technologies for maximum speed and compatibility:

• HTML5 — semantic, accessible markup
• CSS3 — responsive design with custom properties
• Vanilla JavaScript — no frameworks, fast loading
• Google Fonts — Inter & Playfair Display typefaces

No frameworks, no build tools — just HTML, CSS, and JavaScript running directly in the browser. This means CalendarOnline loads fast on any device and works across all modern browsers.

Privacy

We have a firm commitment to your privacy. CalendarOnline does not require registration, account creation, or personal information to use any of its tools. The only external services used are Google Fonts (typography) and Google AdSense (advertising). No personal data is transmitted to our servers. For full details, read our Privacy Policy.

Advertising

We use third-party advertising companies (Google AdSense) to serve ads when you visit calendaronline.live. These companies may use aggregated information about your visits to this and other websites to provide advertisements about goods and services of interest to you. Each individual advertiser is solely responsible for the content of its advertising material. We accept no responsibility for the content of advertising material, including any error, omission, or inaccuracy therein. Advertising revenue helps us keep CalendarOnline free for all users.

Get in Touch

To contact CalendarOnline, use the contact form or send an email:

• General enquiries: contact@calendaronline.live
• Privacy & data: privacy@calendaronline.live
• Website: calendaronline.live