Birth chart guidesMethod and accuracy
Why is my birth chart different on different websites?
By the Hourwyn team
Two websites usually show different birth charts for one of five reasons: a different house system, a time zone or daylight saving difference, a different zodiac (tropical or sidereal), a different city, or a typing slip such as AM for PM. The planets were in one place only, so the cause is almost always a setting or an input.
Match the difference to its cause
| What differs | Likely cause | What to check |
|---|---|---|
| House numbers only. Signs are the same. | House system | Whether each site uses Placidus, Whole Sign, Equal or Koch |
| Rising sign and houses, shifted by about 15° | Time zone or daylight saving, off by one hour | The universal time (UT) each site shows for the birth |
| Almost every planet is one sign earlier | Sidereal zodiac on one site, tropical on the other | The zodiac setting |
| Rising sign is the opposite sign, or close to it | AM and PM swapped | The time you typed |
| Rising degree off by a degree or so | A different city or different coordinates | The latitude and longitude used |
| Lunar node off by about a degree | Mean node on one site, true node on the other | The node setting |
| The list of aspects is longer or shorter | Different orbs, or minor aspects included | The aspect settings |
A quick test
Compare the degree of the Sun and of the Moon on both sites. If they match to within a few hundredths of a degree, both sites used the same moment, and any remaining difference is a setting such as the house system. If the Moon differs by half a degree or more, the two sites disagree about the time, usually by an hour.
Why the time zone step goes wrong
A chart is calculated from universal time, so the site has to know which time zone and daylight saving rule applied at your birthplace on your birth date. Those rules have changed many times. Daylight saving time began in the United States in 1918, was applied town by town for decades, and had its dates changed again in 2007. Today it is not observed in Hawaii or in most of Arizona. Good software looks the answer up in a time zone database. A site that asks you to pick the offset yourself leaves room for a one-hour error.
Which website is the most accurate?
Any site that uses a modern ephemeris and a time zone database puts the planets in the same place to within a small fraction of a degree. Past that point the differences are conventions: which house system, which zodiac, which node, which orbs. A site is trustworthy when it tells you which ones it used.
Common questions
Why is my Moon sign different on another site?
Either the two sites disagree about the time, usually by an hour of daylight saving, or one of them uses the sidereal zodiac. If the Moon was changing sign near your birth time, a small time difference is enough.
Why is my chart different in Vedic astrology?
Vedic astrology uses the sidereal zodiac, which currently sits about 24 degrees behind the tropical zodiac used in Western astrology. Most placements move back one sign.
Why does one site show Chiron or Lilith and another not?
They are optional extra points. Sites choose which to include, and their absence does not make a chart wrong.
My houses match but one planet is in a different house. Why?
The planet is probably within a degree of a house border, and the two sites differ by a few minutes of time or by rounding. Read that placement as belonging to either house.
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Sources
- Daylight Saving Time (DST). National Institute of Standards and Technology (NIST).
- Daylight Saving Time. US Department of Transportation.
- Time Zone Database. Internet Assigned Numbers Authority (IANA).
The guides are written by Hourwyn with the help of AI tools. Astronomical and historical facts are checked against the sources listed under each guide. Astrology is described as a tradition and offered for entertainment. Nothing here is medical, financial, legal or psychological advice.