Why two astrology apps disagree about you

Put the same birth date, time and city into two astrology apps and you can get two different answers. It is unsettling the first time, and the cause is almost always one of four things. None of them is a calculation error.

This is the biggest one, and it moves nearly every planet by about a whole sign. The tropical zodiac measures from the spring equinox; the sidereal zodiac measures from the fixed stars. They lined up roughly two thousand years ago and have drifted about 24° apart since.

Western astrology is tropical. Vedic astrology is sidereal. If your Sun changed from Leo to Cancer between two apps, this is why. Gori is tropical.

Your planets stay where they are but the house lines move, so a planet that was in the tenth becomes a planet in the ninth. This gets worse the further from the equator you were born. Gori uses whole sign.

Without a time, the Ascendant is unavailable and the Moon is uncertain — the midday fallback lands in the wrong sign about 10.8% of the time, measured over 9,600 charts. Two apps making different fallback choices will disagree exactly there.

A wrong time does the same thing more quietly. An hour of error is often a whole sign of Ascendant.

An aspect is a specific angle, and an orb is how far off it can be and still count. There is no standard. Gori uses 8° for conjunctions, 7° for oppositions and trines, 6° for squares and 4° for sextiles — moderate values. An app with wider orbs will list aspects yours does not have, and vice versa.

This is why one app says you have a Sun–Saturn square and another says nothing. Both are describing the same sky.

The useful question is not which is right but which conventions each one is using, and whether it tells you. An app that shows its zodiac, its house system and its orbs is one you can reason about. An app that shows none of them is asking you to take a chart on faith.

Gori states all three, and recalculates your chart from your birth details every time rather than storing a snapshot — so when you correct something, everything downstream corrects with it.