Trust & methodology
Data sources
A birth chart is only as accurate as the data behind it. GetBirthChart relies on three kinds of data: professional ephemeris data for planetary positions, the IANA timezone database for time conversion, and geographic place data for coordinates. Each calculated chart records the ephemeris and timezone data versions used to produce it.
Ephemeris data
Planetary positions are computed from professional ephemeris data by the calculation engine, not approximated in the browser. An ephemeris is a high-precision table of where the Sun, Moon and planets are over time.
Every chart stores the ephemeris provider and data version that produced it, and that provenance is shown in the chart's calculation-metadata section so results stay traceable.
Timezone data
Local birth time is converted to Universal Time using the IANA timezone database, which encodes historical timezone boundaries and daylight-saving rules. This is what lets a chart use the offset that was actually in force at your birth date and place, rather than a single fixed guess.
The timezone data version is recorded alongside each chart.
Place and coordinate data
When you search for a birthplace, GetBirthChart matches it to a place record with latitude, longitude and its IANA timezone. Those coordinates anchor the chart to a point on Earth so the horizon, angles and houses are computed correctly.
What we do not claim
We only describe data we actually use. We do not cite sources we do not rely on, and we do not present interpretive astrological tradition as peer-reviewed science.
For how these inputs flow into a finished chart, see our methodology and calculation guide.
Calculate a chart
See the data sources and versions recorded for your own chart.
Calculate your birth chart