Understanding Birth Information in Astrology

Our Love Compatibility Tool asks for a date of birth, an optional time of birth, and a city. Here’s what each of those is actually doing, and why time in particular changes the result more than it might seem like it should.

Date of birth: the Sun and Moon’s position

The date fixes roughly where the Sun and Moon were on the day you were born — your sun sign, and a close approximation of your moon sign. This is what a lighter tool like a Zodiac Guide works from, and it’s genuinely useful for a general read on emotional style and temperament.

Time of birth: the Ascendant, and a more precise Moon

The Moon moves roughly 13 degrees a day — about half a degree an hour — which means it can shift from one sign into the next during a single day. Without an accurate time, there’s a real chance the calculation lands on the wrong moon sign entirely if your birth happened near that boundary.

Time of birth also determines the Ascendant (rising sign) — the sign on the eastern horizon at the moment you were born — which shifts roughly every two hours. The Ascendant anchors the entire house system a chart is built from, including which house Venus, Mars, and the other planets fall into. Without it, calculations that depend on house placement (like the manglik/Kuja dosha check inside our Compatibility Tool) default to an assumed time, which is why we’re upfront whenever that default gets used instead of your real birth time.

Place of birth: latitude, longitude, and local time

The Ascendant and house positions also depend on exactly where on Earth you were born, not just when — the same moment in time produces a different Ascendant in Chennai than it does in Delhi. Place of birth also resolves which local time zone and daylight-saving rules applied, which matters for converting your birth time into the precise astronomical moment the calculation actually runs on.

If you don’t know your exact birth time

It happens — not everyone’s birth certificate or family records include it. Our Compatibility Tool will still run with a default time if you leave it blank, but the result will be less precise for anything that depends on the Ascendant specifically. If precision matters for your situation, it may be worth asking family members, checking a birth certificate, or asking the hospital you were born in for records, before relying heavily on time-sensitive parts of a reading.