Zodiac Sign Calculator
This calculator maps a valid birth date to a Western sun sign using a fixed month-and-day lookup table evaluated in UTC. It does not calculate an astronomical chart; the same month and day always return the same sign here. For entertainment, not a scientific assessment.
Last updated · View algorithm, constants and default inputs (JSON)
Results
About this calculator
This calculator maps a valid birth date to a Western sun sign using a fixed month-and-day lookup table evaluated in UTC. It does not calculate an astronomical chart; the same month and day always return the same sign here. For entertainment, not a scientific assessment.
Worked example
calculated with the default values below
Date of birth 1990-06-15 Western Sun sign Gemini
Method and assumptions
The calculator reads the UTC month and day of a valid date, then selects a Western Sun sign from a fixed boundary table. Birth year does not change these boundaries. It does not use a location, historical time-zone database or astronomical ephemeris, and it does not calculate an ascendant. Dates near an astronomical sign transition may therefore differ from a birth chart.
Disclaimer
For entertainment, not a scientific assessment.
Implementation source
This record describes the implementation used by this page. It is not independent validation. External references, when available, support only the stated formula or definition; estimates and custom rules retain their own assumptions.
Formula and variables
K = month × 100 + day; sign = fixedThresholdLookup(K)
- month
- Birth month (1–12)
- day
- Birth day
- K
- Month-day code
- sign
- Western sun-sign label
A fixed month-and-day threshold table is evaluated using the UTC date input. This is not an astronomical ephemeris; the same month and day always map to the same sign.
Frequently asked questions
Does the sign vary by birth year or time zone?
This calculator uses a fixed UTC month-and-day lookup table, so a given month and day always maps to the same sign. It does not account for birth time, location, or year-specific astronomical positions.