Why two programs show different charts

Check the input first

More than half of all differences happen before any calculation. Check three things. The date: 03/04 is 3 April in most of the world and 4 March in the US. The time: the 12-hour clock confuses midnight with noon. The place: many towns share a name with places in other states or countries, and the coordinates set both the rising sign and the time zone.

Why this matters so much: the lagna moves about one degree every four minutes and changes sign roughly every two hours. A 15-minute error moves it almost 4°, and near the edge of a sign it changes the whole house count.

Cause 1. Tropical or sidereal zodiac

Western astrology counts the signs from the spring equinox; Jyotish counts them from the stars. The difference is the ayanamsha, about 24°13′ in 2026. So if every planet in one chart is almost a sign behind the other, one of the programs is tropical. For about four people in five the Sun falls in the previous sign in a Vedic chart. More in why my Vedic sign is different.

Cause 2. Different ayanamshas

Even within Jyotish there is no single ayanamsha. Lahiri is the most widely used; in 2026 the Raman ayanamsha is 1°27′ smaller, the KP ayanamsha 6′ smaller. A shift of 1.5° changes the Moon's nakshatra for roughly one person in nine — those whose Moon sits near a nakshatra boundary.

The ayanamsha matters most for the dashas. The balance of the first dasha is measured by the Moon's position inside its nakshatra, and every arc-minute is worth several days: with the Moon in a Venus nakshatra (a 20-year dasha), one minute shifts every date by about 9 days. Lahiri versus KP gives up to two months; Lahiri versus Raman about two years. Which one to choose is covered in the article on the ayanamsha.

Cause 3. Time zone and daylight saving on the birth date

A program must use the offset from Greenwich that was in force at the birthplace on that day, not today's. Clock history is messy: India kept “war time”, UTC+6:30, from 1942 to 1945; the USSR ran its clocks an hour ahead of the zone from 1930 and added summer time from 1981; Almaty in Kazakhstan moved from UTC+6 to UTC+5 in March 2024. A program with an outdated or simplified time zone database is off by an hour. An hour is about 15° of lagna — nearly always a different sign — and half a degree of Moon.

The tell-tale sign: the lagna and houses differ while the planets agree to the minute.

Cause 4. True node or mean node

Rahu and Ketu are mathematical points, and there are two ways to compute them: the mean node moves smoothly, the true node follows the wobble of the Moon's orbit. They differ by up to 1.5°, so Rahu's sign-change dates differ by days between programs, and sometimes Rahu's nakshatra differs too. More in the article on Rahu and Ketu.

Cause 5. The house system

Classical Jyotish uses whole-sign houses: the whole lagna sign is the 1st house, the next sign the 2nd, and so on. Some programs also show a bhava chalit chart (houses measured from the degree of the lagna), where a planet near the edge of a sign moves into the neighbouring house. KP builds houses from Placidus cusps. None of this is an error — it is a different question asked of the chart; just know which table you are reading.

Cause 6. Dasha year length and vargas

Even with the same ayanamsha, dasha dates can drift because of the length of the “year”: some programs use the sidereal year (about 365.26 days), some 365.25 days, some a 360-day year. Between 365.26 and 360 days the gap exceeds six months over 40 years.

Divisional charts are also computed in different ways: D9 has one rule, but the drekkana (D3) and hora (D2) have several classical variants. If only one varga disagrees, check its method in the settings. On the vargas themselves, see divisional charts.

Cause 7. Ephemeris and rounding

Modern programs use precise ephemerides, NASA JPL's among them; the differences between them are fractions of an arc-second and do not affect the chart. Visible errors come only from old tables and from rounding: if a program drops the minutes or seconds of the birth time, a Moon near a nakshatra boundary can jump across it.

How to compare two charts in five minutes

1. Make sure the date, time and place are entered identically, and check which offset from UTC each program applied. 2. Compare the zodiac and the ayanamsha each program uses (its value in degrees is usually shown under “technical data”). 3. Compare the Moon's degree to the minute — the nakshatra and the dashas depend on it. 4. Compare the lagna degree. 5. Check the node type and the house system. Only when these five match does it make sense to compare interpretations.

How JyotiSoft calculates

JyotiSoft calculates in the sidereal zodiac with the Lahiri ayanamsha, the true node for Rahu and Ketu, whole-sign houses and the sidereal year for dashas. The time zone and daylight saving are taken for the birthplace on the exact date from the time zone database. The calculation is checked against Jagannatha Hora on reference charts. You can draw the chart in North or South Indian style — the content does not change; see chart styles.

Questions

See also

• Ayanamsha
• Why my sign is different
• Birth chart without a birth time
• Nakshatra calculator
• How we calculate and write
• Free Kundli (birth chart)
• KP and the Parashari school

Positions and tables: sidereal zodiac, Lahiri ayanamsha — the same as professional Jyotish astrologers use, and the same calculation as the charts in JyotiSoft. Updated 2026-10-13.