Hindu Lunar Calendar & Tithi Converter
The Hindu Lunar Calendar: Ancient Timekeeping and Tithis
The Hindu or Vedic calendar is a lunisolar system that has been used in India for millennia to track religious festivals, auspicious dates, and life milestones. Unlike the solar Gregorian calendar used internationally, the Hindu calendar is based on lunar months (from new moon to new moon) and divides each month into 15 lunar days called "tithis." Each tithi corresponds to a specific angular separation between the Moon and Sun. Understanding the Hindu calendar requires knowledge of lunar phases, which differ from the Gregorian date, making conversion essential for Hindi/Sanskrit scholars, Hindu practitioners, and those planning spiritual or cultural events aligned with lunar cycles.
The calendar is officially known by the Vikram Era (Vikram Samvat), where the year numbering differs from the Gregorian calendar. Year 2024 CE is approximately Vikram Samvat 2081. Religious festivals like Holi, Diwali, Dussehra, and Ramnavami are celebrated on specific tithis, ensuring they occur on spiritually and astronomically significant dates regardless of Gregorian month.
Tithi Definition and Lunar Phase Relationship
A tithi is defined as the time required for the Moon to advance 12° in its orbit relative to the Sun, corresponding to 1/30th of a lunar month. The relationship is:
where the lunar phase angle is the geocentric elongation (angular distance between Sun and Moon). New moon is 0°; full moon is 180°. Tithis are grouped into two fortnights: the bright fortnight (Shukla Paksha, new moon to full moon, tithis 1–15) and dark fortnight (Krishna Paksha, full moon to new moon, tithis 1–15 again). The cycle repeats every ~29.5 days, so a Hindu month is typically 29–30 days, not aligned with Gregorian months.
Worked Example: Converting December 25, 2024
A person born on December 25, 2024 (Christmas) wants to know the Hindu calendar equivalent for astrological purposes. Conversion:
Step 1: Determine lunar phase on Dec 25 – Astronomical calculation: ~3° from new moon (occurs Dec 22, 2024), early in Shukla Paksha. Tithi ≈ 1 or 2 (Pratipada).
Step 2: Identify Hindu month – Dec 25 falls in the month of Pausa (Vikram calendar), which corresponds roughly to Dec-Jan.
Step 3: Calculate Vikram year – 2024 CE + 57 = 2081 Vikram Samvat (approximately).
Result:** December 25, 2024 = Pausa Shukla Pratipada, Vikram Samvat 2081 (or similar, depending on precise astronomical data).
Hindu Lunar Months and Gregorian Month Overlap
| Hindu Month (Lunar) | Vikram Calendar Period | Gregorian Overlap | Significance |
|---|---|---|---|
| Chaitra | Starting Vikram Year | Mar–Apr | Spring; Hindu New Year |
| Vaishakh | Apr–May | Akha Teej, Vat Purnima | |
| Jyeshtha | May–Jun | Ganga Dussehra | |
| Ashadh | Jun–Jul | Ratha Yatra | |
| Shravan | Jul–Aug | Janmashtami, Nag Panchami | |
| Bhadr | Aug–Sep | Krishna Janmashtami, Radha Navami | |
| Ashwin | Sep–Oct | Navratri, Dussehra, Diwali | |
| Kartik | Oct–Nov | Diwali, Govardhan Puja | |
| Margshirsh | Nov–Dec | ||
| Pausa | Dec–Jan | Makar Sankranti (Jan 14) | |
| Magha | Jan–Feb | Basant Panchami | |
| Phalguna | Feb–Mar | Holi |
Hindu months do not align perfectly with Gregorian months because lunar cycles are ~29.5 days while Gregorian months are ~30.4 days. Over years, lunar calendars "drift" relative to solar calendars, requiring intercalation (adding extra months called Adhik Maas).
Using the Calculator
Enter any Gregorian date and timezone. The calculator estimates the corresponding Hindu lunar month (Chaitra through Phalguna), tithi number (1–15), and phase (Shukla or Krishna Paksha), plus the approximate Vikram year. Note: precise conversions require detailed astronomical ephemeris; this calculator provides estimates suitable for general cultural and informational purposes.
Limitations
Hindu calendar conversions are complex, involving astronomical calculations of the Moon's position relative to the Sun. Different regions of India historically used slightly different calendar systems, and modern standardization varies. Precise conversions require consulting official Hindu calendar almanacs (Panchang) published for specific regions and years. This calculator provides approximate conversions; for religious ceremonies or astrological purposes, consult a qualified Vedic astrologer or published Panchang for your region.