A THOUGHTFUL PLACE TO BEGIN
Why do charts sometimes differ?
Jyotisha has been practiced across many communities and schools. They may use different reference points, calculation methods, or calendar rules. Two carefully made charts can therefore differ even when the birth details are the same.
If you have a family astrologer or an existing chart, ask which settings were used. Otherwise, our Lahiri default is a practical starting point. Your interface language does not determine your tradition.
This guide explains calculation choices and their stated uses. Astrological interpretations are traditional beliefs; choosing a setting does not establish that its predictions are scientifically proven.
THE SIDEREAL ZODIAC
Understanding ayanamsa
A tropical zodiac measures from the moving equinox; a sidereal zodiac uses a reference related to the stars. An ayanamsa defines the offset used to express positions in a sidereal zodiac. Different definitions can move a planet across a sign, nakshatra, or pada boundary, and can shift dasha timings. Differences are usually most consequential when a placement is close to a boundary.
What you gain
Choose the reference point used by a school or by the chart you want to compare.
What to consider
A shared name is not always a complete definition. Epoch, precession, nutation and star calculations can differ between products.
Ayanamsas available in Jotish
These are calculation choices, not endorsements. Expand a group to see when it may be useful and where comparisons need care.
Lahiri & Chitra PakshaOur default and related definitions
Lahiri (IMD) is our default and a useful starting point when comparing with modern Indian astronomical references. The Lahiri 1940 / IAU 2006 option uses a separately specified historical anchor. True Chitra (geometric) anchors to a star rather than the same epoch formula.
Tradeoff: “Lahiri,” “Chitra Paksha,” and “True Chitra” are not automatically interchangeable. Star catalogue and geometric-versus-apparent choices can affect a comparison. Read the IMD's explanation ↗
Krishnamurti (KP)IAU 2006, published table, KP New and linear
KP practitioners may use different ayanamsa formulas. Jotish offers Krishnamurti IAU 2006, a separate published-table anchor, KP New (Balachandran 2003) and a distinct 1900 linear formula.
Tradeoff: Choose the exact formula used in your reference chart. KP packages select Placidus cusps and display star and sub lords. They do not yet implement all KP interpretive rules or every KP software variant. Read the published formula collection ↗
Raman, Yukteshwar & J. N. BhasinNamed reference-epoch and published-table traditions
The Raman, Yukteshwar (IAU 2006) and J. N. Bhasin starting points use specified reference anchors with IAU precession and nutation. A separate Yukteswar published-table option uses an annual 54″ rate and does not add nutation.
Tradeoff: The two Yukteswar options follow different definitions and can give noticeably different results. A historic table or another program may use another reference frame or revision; a name alone cannot guarantee a match. The published table's annual values have been checked, but its complete chart conventions have not.
Pushya, Chitra & RevatiGeometric star-based definitions
These choices define the reference using a particular star. Pushya-paksha follows a published proposal associated with P. V. R. Narasimha Rao; geometric Chitra and Revati use their respective reference stars.
Tradeoff: Jotish's definitions are geometric and do not include annual aberration or parallax. An apparent-star method or a different catalogue may produce a different offset. Read the Pushya-paksha proposal ↗
Other named & custom choicesDe Luce, Ushashashi, Fagan-Bradley and more
Jotish also offers De Luce (historical anchor and modern adjustment), Ushashashi, Djwhal Khul, and Fagan-Bradley, plus custom IAU reference, geometric-star and historical polynomial definitions.
Tradeoff: Some are comparison options used outside mainstream Indian practice. Custom methods require the source's exact epoch, units and frame; they cannot automatically reproduce every historical model.
THE LUNAR NODES
Mean or true Rahu?
Rahu and Ketu represent opposite lunar nodes. The mean node follows a smoothed model; the true node follows an instantaneous osculating lunar orbit and can briefly move forward as well as backward.
Mean node
Useful for: traditions and chart software using a smoothed position.
Consider: different mean-node formulas still differ. Our default is IERS 2010.
True node
Useful for: a reference chart that specifies an osculating true node.
Consider: it will not always match a mean-node chart, especially near a boundary.
An experimental Swiss-comparison mean-node fit is available for 1900–2050. It is a comparison aid, not a separate traditional school.
PLANETARY POSITIONS
Planet center or system center?
For Jupiter and Saturn, Jotish can calculate positions using the center of the planet or the center of mass of the planet-and-moon system. The positions are close but not identical.
Planet center
Useful for: a chart that uses each planet's own center.
Consider: a system-barycenter reference can differ slightly.
System barycenter
Useful for: comparisons with software using the combined system center.
Consider: a small difference may matter near a sign or nakshatra boundary.
This setting applies to Jupiter and Saturn. Jotish's current Mars position uses the Mars-system barycenter. It does not change the selected ayanamsa or implement a different panchang tradition.
THE RHYTHM OF TIME
How long is a dasha year?
Vimshottari periods are expressed in years, but software can convert those years into dates using different year lengths. This choice changes period start and end dates; small differences accumulate over long periods.
The API also accepts a custom year length from 350 to 370 days. Match the source before comparing dates; none of these choices proves an interpretation.
PLACE, SUNRISE & CLOCK
Where and when matter
A panchang day and its weekday usually turn over at sunrise. Jotish supports two definitions: the visible upper limb with standard refraction, and the unrefracted geometric center at the horizon. Their different sunrise times can change the weekday or limb assigned near dawn.
Jotish determines the time zone from the selected location. For some historical places and dates, records may reflect more than one local clock; the chart can show a known alternative when relevant.
The calculations use a sea-level observer and a standard refraction model where selected. Real elevation, weather and local horizon can differ; a recorded birth time may itself be approximate.
CALENDARS & TRADITIONS
Different panchang systems
A panchang describes five limbs: vara, tithi, nakshatra, yoga and karana. The method used for planetary positions is one choice; calendar-month naming and festival rules are separate choices.
Drik / astronomical panchang
Our current five-limb panchang uses modern Sun and Moon positions. It has been checked against selected published Indian panchang examples.
The checks cover specific dates and conventions. They do not establish agreement with every publisher, location or date.
Vākya & siddhānta methods
Some almanacs follow traditional tables and calculations. Vākya requires its own calculation method, and different published lineages may apply different corrections.
We are researching and testing these methods. A complete Vākya or Sūrya Siddhānta panchang is not yet selectable.
Regional calendar rules
Amānta and Pūrṇimānta lunar months and regional solar calendars use different month boundaries or naming. The Indian government publishes regional reference tables.
Complete lunar months, regional calendars and festival determination are not yet implemented. Language or location alone does not determine a person's practice.
Explore the IMD Rashtriya Panchang explanation ↗ and its regional calendar tables ↗.
MAKE IT YOURS
Choosing a starting package
Our packages combine an ayanamsa, node and dasha year as an editable starting point. You can adjust individual settings in the birth chart form. KP packages select Placidus cusps; you can also choose whole-sign houses. A package describes its settings; it does not claim to cover every practice in a school.
- 01Have a chart to match?
Use its stated method, ayanamsa, node, year length and birth details where known.
- 02Follow an astrologer or family tradition?
Choose the method they use. The same language or region can have multiple practices.
- 03Just beginning?
Start with Lahiri, mean node and the default dasha year. You can revise these settings as you learn.
KEEP EXPLORING
Sources & further reading
Our guide is grounded in published methods and examples. The sources describe particular systems; they do not establish that all practitioners follow the same rules.