How FateChart Calculates Your Chart

A birth chart is only as honest as the math behind it. Two sites can take the same birthday and hand you two different charts — usually because they quietly disagree about time zones, solar time, or which calendar a date belongs to. We would rather show our work than ask you to trust a black box.

Here is exactly how FateChart turns your birth details into a chart.

What we ask for, and why

We need three things: your date of birth, your time of birth, and your place of birth.

• Date and time fix the positions of the Sun, Moon, and planets, and (for BaZi and Zi Wei Dou Shu) the hour pillar and star placements.
• Place does two jobs: it gives us the latitude and longitude for the house calculation, and it tells us which time zone — including any historical daylight-saving rule — was in force at that moment.

Your birth place is used for the calculation only. You can generate a free chart without creating an account, and we never sell your data.

Time zones are the most common source of error

A chart stands or falls on getting the moment right in Universal Time. The trap is daylight-saving and historical time-zone changes: the offset for a city in 1985 is often not the offset it uses today.

We resolve the time zone from the place and the date together, not from the country alone, using the standard IANA time-zone database (the same one your phone and operating system use). That means a birth during a summer-time period is converted with the summer offset, and a birth in a region that has since redrawn its zone boundaries is converted with the rule that applied then.

True solar time vs. clock time

Clock time is a political convenience — a whole region shares one offset. The sky does not. True solar time is local noon defined by the Sun actually crossing your meridian, and it can sit 15–45 minutes away from your clock, depending on how far you are from the centre of your time zone and the time of year.

This matters most for the Eastern systems:

• BaZi (八字) divides the day into twelve two-hour branches. A birth near the boundary of a branch can fall into the neighbouring hour pillar once true solar time is applied.
• Zi Wei Dou Shu (紫微斗数) likewise keys the hour palace to the solar hour.

Where it changes the result, we compute true solar time from your longitude. For Western charts the effect is smaller — house cusps shift slightly — but we use the precise moment all the same.

The lunar calendar and the Eastern systems

BaZi and Zi Wei Dou Shu are rooted in the Chinese calendar, but not in the same way.

• BaZi is solar: the year pillar turns at Lì Chūn (立春, the start of spring around 4 February), not at Chinese New Year, and the month pillars follow the 24 solar terms. A baby born in late January belongs to the previous BaZi year even though the Gregorian year has changed.
• Zi Wei Dou Shu uses the lunar date — the lunar month and day — so we convert your solar birthday to its lunar equivalent, including the handling of leap months.

We do these conversions with an astronomical ephemeris, not a lookup table, so dates far in the past or future stay accurate.

If you don't know your birth time

An unknown or approximate birth time is common, and it doesn't make a chart useless — it just limits what can be said with confidence.

• The Rising sign (Ascendant) and the house cusps depend directly on the time and rotate roughly one degree every four minutes, so without a time we don't fabricate them.
• The Moon can move up to ~15° in a day, so its sign is usually safe but its exact degree may be uncertain.
• For BaZi, the hour pillar is the part you lose without a time; the year, month, and day pillars still stand.

When a time is missing, FateChart is explicit about which parts of the reading are reliable and which are not — rather than presenting a guess as fact.

Which schools we follow

Astrology is not one tradition, and reasonable practitioners differ. We pick widely used, defensible defaults and tell you which:

• Western: the tropical zodiac (aligned to the seasons, the standard in modern Western astrology) with Placidus houses, the most common house system in contemporary practice.
• BaZi: the orthodox solar-term calendar for the four pillars, with the day master and five-element balance as the backbone of the reading.
• Zi Wei Dou Shu: the mainstream San He / Zhong Zhou-style star placements across the twelve palaces.

Where a respected alternative exists (sidereal zodiac, whole-sign houses, the Flying Stars Zi Wei variant), the difference is one of interpretation, not of arithmetic — our calculations are transparent enough that you can compare.

What a FateChart reading is — and isn't

Everything above is deterministic mathematics: given the same inputs, the chart is always the same, and you could reproduce it with any reputable ephemeris.

The interpretation is a separate layer. We use AI to put the chart into plain language, and we label it as AI-generated. It is written to help you reflect — on patterns, timing, and tendencies — not to predict fixed events or replace professional advice. The chart is the fact; the reading is a perspective on it.

Questions about a specific calculation? Email contact@aijentra.com — we're happy to walk through exactly how your chart was built.