Lunar Calendar Options
When generating lunar-based mundane charts — new lunar month charts, Chaitra Shukla Pratipada, or paksha charts — several calendar conventions must be specified. The choice of month definition, month naming, and year-start convention affects which charts are generated and how they are interpreted.
Lunar Month Definition
Two competing traditions define when a lunar month begins and ends:
Amanta (New Moon to New Moon)
- Standard definition; most widely used in mundane astrology
- Each month starts at the exact Sun–Moon conjunction (Amavasya)
- Month ends at the next New Moon
- Predominant in South India and in most software defaults
Purnimanta (Full Moon to Full Moon)
- Traditional North Indian usage
- Each month starts at the Full Moon (Purnima)
- Month ends at the next Full Moon
- The month carries the name of the nakshatra where the Full Moon falls
Month Naming Convention
The twelve lunar months receive names (Chaitra, Vaishakha, etc.) according to one of two systems:
Sidereal Signs (Standard)
- Month names based on the sidereal sign the Sun occupies at New Moon
- Most popular and widely used system in modern software
- Example: Sun in sidereal Pisces at New Moon → Chaitra month
Tropical Signs (Parasara / PVR Rao)
- Month names based on the tropical sign the Sun occupies at New Moon
- Taught by Parasara in the Vishnu Purana
- Recommended by PVR Rao for Tithi Pravesha — keeps months aligned to actual seasons
- Produces better seasonal alignment for agricultural and weather predictions
The Twelve Lunar Months
The Vedic lunar year consists of twelve named months, each governed by a specific sidereal sign position:
| # | Lunar Month | Sun's Sidereal Sign at New Moon | Approximate Period |
|---|---|---|---|
| 1 | Chaitra | Pisces | March – April |
| 2 | Vaishakha | Aries | April – May |
| 3 | Jyeshtha | Taurus | May – June |
| 4 | Ashadha | Gemini | June – July |
| 5 | Shravana | Cancer | July – August |
| 6 | Bhadrapada | Leo | August – September |
| 7 | Ashvina | Virgo | September – October |
| 8 | Kartika | Libra | October – November |
| 9 | Margashirsha | Scorpio | November – December |
| 10 | Pausha | Sagittarius | December – January |
| 11 | Magha | Capricorn | January – February |
| 12 | Phalguna | Aquarius | February – March |
Start of Lunar Year
Two main conventions exist for when the Vedic lunar year begins:
Chaitra (Pisces) — Standard
- Vedic lunar year begins at the New Moon in sidereal Pisces (Chaitra Shukla Pratipada)
- This is the most widely accepted starting point in Indian tradition
- Corresponds to spring — the natural new year in most Indian regional calendars
Regional Variants
- Configurable in most Jyotish software to accommodate regional calendar variations
- Some traditions begin the year from Kartika (Diwali) or Margashirsha
- The choice of year-start affects which chart is considered the "primary" lunar year chart
The choice of lunar calendar convention is not merely a formatting preference — it determines which New Moon is treated as the year's starting chart and how month names are assigned, which in turn affects the interpretation of annual themes for collective predictions. Most mundane astrologers follow the Amanta system with sidereal month naming as the standard, while tropical naming is recommended for Tithi Pravesha and seasonal predictions.