What is the Lunar Calendar?
The lunar calendar is a traditional calendar system used across East Asia, based on the cycles of the Moon. Unlike the solar (Gregorian) calendar used worldwide, the lunar calendar tracks months by lunar phases, with each month beginning on a new moon.
This tool provides an interactive lunar calendar that displays both solar and lunar dates together, making it easy to look up important dates, traditional holidays, and almanac information at a glance.
Who Uses the Lunar Calendar?
The lunar calendar remains widely used in daily life across several cultures:
Vietnamese
Chinese
Korean
What This Tool Offers
Our Lunar Calendar tool brings traditional almanac information into a modern, easy-to-use interface:
Dual Date Display
See solar and lunar dates side by side on every calendar cell
Can Chi System
View the Heavenly Stems and Earthly Branches for each year, month, and day
Zodiac Animals
Identify the zodiac animal for any year with visual icons
Solar Terms
Track the 24 seasonal divisions important in agriculture and traditional practices
Auspicious Hours
Check daily Hoang Dao (auspicious) and Hac Dao (inauspicious) hours
Day Quality
Quickly identify good and bad days based on traditional calculations
Multi-Locale Support
Automatically adapts terminology and holidays based on your language
- 1. What is the Lunar Calendar?
- 2. How to Use the Lunar Calendar
- 3. Features
- 4. Frequently Asked Questions
- 4.1. What is the difference between the solar and lunar calendar?
- 4.2. What does Can Chi mean?
- 4.3. What are Hoang Dao and Hac Dao?
- 4.4. Why does Vietnam use the Cat instead of the Rabbit?
- 4.5. What are Solar Terms?
- 4.6. How accurate are the lunar date calculations?
- 4.7. Can I look up dates far in the past or future?
- 4.8. Does the calendar work offline?
How to Use the Lunar Calendar
Viewing Today's Information
When you first open the calendar, the Today Card at the top shows the current date with both solar and lunar information. The left side displays the solar (Gregorian) date, while the right side shows the lunar date along with Can Chi details, zodiac animal, and the current solar term.
Navigating Months
The toolbar provides several ways to navigate:
- Arrow buttons — Click the left or right arrows to move one month at a time
- Month dropdown — Select any month from the dropdown menu
- Year input — Click the year field and type a year, or select from the dropdown list
- Today button — Quickly return to the current month and date
Viewing Day Details
Click any date on the calendar grid to open a detailed view. The detail panel shows:
Date Information
- Full lunar date with Can Chi for year, month, and day
- The governing duty (Truc) and its quality rating
- The day's celestial star and road classification
- Solar term information (if applicable)
Daily Guidance
- All 12 daily hours with their auspicious/inauspicious status
- Recommended activities for the day
- Discouraged activities to avoid
Day Quality Indicator
Click the Day Quality button in the toolbar to toggle a color overlay on the calendar grid. Days are highlighted with a subtle green background for auspicious days and a subtle red background for inauspicious days, based on the Hoang Dao / Hac Dao system.
Auspicious Hours
The hours section at the bottom of the page displays all 12 traditional Chinese hours (Canh Gio) for the currently viewed day. Each hour shows its Can Chi name, time range, celestial deity, and whether it is auspicious (Hoang Dao) or inauspicious (Hac Dao).
Keyboard Shortcuts
| Shortcut | Action |
|---|---|
| ← Left Arrow | Previous month (or previous day when detail panel is open) |
| → Right Arrow | Next month (or next day when detail panel is open) |
| Esc Escape | Close the detail panel |
Features
Dual Calendar Display
Every cell in the calendar grid shows both the solar date and the corresponding lunar date. Special lunar dates are clearly marked: the 1st of each lunar month displays a month indicator, and the 15th (full moon) is labeled separately. Solar terms and traditional holidays appear directly on the relevant cells.
Gregorian Calendar
- Based on Earth's orbit around the Sun
- Fixed month lengths (28-31 days)
- Widely used internationally
Lunar Calendar
- Based on Moon's phases
- Variable months (~29.5 days)
- Traditional East Asian system
Can Chi (Heavenly Stems & Earthly Branches)
The Can Chi system combines 10 Heavenly Stems with 12 Earthly Branches to create a 60-year cycle used throughout East Asian calendrics. The tool calculates and displays the Can Chi designation for the year, month, and day in your chosen locale — whether that is Vietnamese (Giap Ty), Chinese (甲子), or Korean (갑자).
Zodiac Animals
Each lunar year is associated with one of 12 zodiac animals. The Today Card prominently displays the zodiac animal for the current year with a visual icon. Note that Vietnam uses the Cat in place of the Rabbit, which is reflected when viewing in Vietnamese.
Rat
Ox
Tiger
Rabbit / Cat
Dragon
Snake
Horse
Goat
Monkey
Rooster
Dog
Pig
Solar Terms (Tiet Khi)
The 24 solar terms divide the year based on the Sun's position along the ecliptic. These markers are essential for agriculture and traditional practices. The calendar highlights days that fall on a solar term, and the Today Card shows the current solar term period.
Auspicious & Inauspicious Hours
Each day is divided into 12 traditional hours (Canh Gio), each governed by a celestial deity. Six hours are classified as Hoang Dao (auspicious) and six as Hac Dao (inauspicious). The hours section provides a clear visual grid showing the quality of each time period along with its Can Chi designation.
Yellow Road - Favorable Hours
Hoang Dao hours are governed by benevolent celestial deities and are considered favorable for important activities:
- Thanh Long (Azure Dragon) — Excellent for new beginnings
- Minh Duong (Bright Hall) — Ideal for ceremonies and meetings
- Kim Quy (Golden Turtle) — Good for financial matters
- Thien Duc (Heavenly Virtue) — Favorable for all activities
- Ngoc Duong (Jade Hall) — Auspicious for celebrations
- Tu Menh (Commanding) — Good for leadership decisions
Black Road - Unfavorable Hours
Hac Dao hours are governed by less favorable deities and are generally avoided for important undertakings:
- Thien Hinh (Heavenly Punishment) — Avoid legal matters
- Chu Tuoc (Vermillion Bird) — Unfavorable for negotiations
- Bach Ho (White Tiger) — Caution with conflicts
- Thien Lao (Heavenly Prison) — Avoid restrictions
- Huyen Vu (Black Tortoise) — Not ideal for travel
- Cau Tran (Hook and Twist) — Beware complications
Day Quality Overlay
Toggle the Day Quality feature to see at a glance which days in the month are auspicious or inauspicious. The system uses the Hoang Dao / Hac Dao classification based on the day's governing celestial deity.
Hac Dao (Red Background)
- Governed by unfavorable deities
- Avoid major decisions
- Not ideal for important events
Hoang Dao (Green Background)
- Governed by benevolent deities
- Favorable for new ventures
- Ideal for celebrations
Traditional Holidays
Lunar holidays are automatically displayed based on your locale. Vietnamese users see Tet Nguyen Dan, Gio To Hung Vuong, and Vu Lan. Chinese users see Spring Festival, Dragon Boat Festival, and Mid-Autumn Festival. Korean users see Seollal, Dano, and Chuseok.
Vietnamese Holidays
- Tet Nguyen Dan (Lunar New Year)
- Gio To Hung Vuong (Hung Kings' Festival)
- Vu Lan (Ullambana Festival)
- Tet Trung Thu (Mid-Autumn Festival)
Chinese Holidays
- Spring Festival (Chinese New Year)
- Lantern Festival
- Dragon Boat Festival
- Mid-Autumn Festival
Korean Holidays
- Seollal (Lunar New Year)
- Daeboreum (First Full Moon)
- Dano (Spring Festival)
- Chuseok (Harvest Festival)
Multi-Locale Support
The calendar automatically adapts all terminology, holiday names, Can Chi translations, and zodiac designations based on your language setting. Supported locales include Vietnamese, Chinese (Simplified), and Korean.
Automatic Adaptation
All text, terminology, and cultural references automatically adjust to your selected language
Localized Holidays
Traditional holidays specific to each culture are displayed accurately
Cultural Accuracy
Can Chi names, zodiac animals, and celestial deities use authentic local terminology
Server-Side Rendering
The initial calendar view is rendered on the server for fast loading and search engine visibility. Subsequent navigation is handled dynamically for a smooth, app-like experience.
Frequently Asked Questions
What is the difference between the solar and lunar calendar?
The solar (Gregorian) calendar is based on Earth's orbit around the Sun, with fixed month lengths. The lunar calendar is based on the Moon's phases, with each month starting on a new moon.
A lunar month is approximately 29.5 days, so the lunar year is about 11 days shorter than the solar year. Leap months are periodically inserted to keep the lunar calendar aligned with the seasons.
What does Can Chi mean?
Can Chi (also known as Gan Zhi in Chinese) is a traditional system that combines 10 Heavenly Stems (Can/Gan) with 12 Earthly Branches (Chi/Zhi) to create a repeating 60-unit cycle.
This system is used to designate years, months, days, and hours in East Asian calendrics and astrology. Each combination carries specific meanings and influences in traditional fortune-telling and almanac practices.
What are Hoang Dao and Hac Dao?
Hoang Dao (Yellow Road) refers to auspicious time periods governed by benevolent celestial deities such as Thanh Long (Azure Dragon) and Minh Duong (Bright Hall). These periods are considered favorable for important activities, ceremonies, and new ventures.
Hac Dao (Black Road) refers to inauspicious periods governed by less favorable deities. This system applies to both daily hours and entire days, helping people choose optimal timing for significant events.
Why does Vietnam use the Cat instead of the Rabbit?
In the Vietnamese zodiac, the fourth animal is the Cat (Meo) rather than the Rabbit used in Chinese and Korean traditions. The exact historical reason is debated, but one common theory relates to the similar pronunciation of the Earthly Branch "Mao" (卯) and the Vietnamese word for cat.
Another theory suggests that cats were more culturally significant in Vietnam's agrarian society, where they protected rice stores from rodents, making them more relevant than rabbits.
What are Solar Terms?
Solar terms (Tiet Khi in Vietnamese, Jieqi in Chinese) are 24 points in the year based on the Sun's position along the ecliptic. They mark seasonal transitions and are traditionally used to guide agricultural activities.
Examples include:
- Lap Xuan (Start of Spring) — Beginning of spring season
- Ha Chi (Summer Solstice) — Longest day of the year
- Dong Chi (Winter Solstice) — Shortest day of the year
- Xuan Phan (Spring Equinox) — Equal day and night in spring
How accurate are the lunar date calculations?
This tool uses the well-established 6tail/lunar-php astronomical calculation library, which provides highly accurate lunar calendar data covering a wide range of years.
The calculations account for leap months, varying month lengths, and regional differences. The library is based on precise astronomical algorithms used in traditional Chinese calendar systems.
Can I look up dates far in the past or future?
Yes. You can navigate to virtually any year using the year input field. Simply type the desired year and press Enter, or select from the dropdown.
The calendar will display accurate solar and lunar date mappings for the selected period, making it useful for historical research, future planning, or checking birth dates and anniversaries.
Does the calendar work offline?
The initial calendar page loads with full data rendered by the server, so you can view the current month immediately upon loading.
However, navigating to different months or viewing day details requires an internet connection to fetch the corresponding data from the server. This approach balances performance with comprehensive functionality.
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