Sun Sign Calculator

Your Sun sign is the zodiac sign the Sun occupied at the moment you were born, and it is the sign people mean when they ask what you are. It is read as your core identity: the drive that shapes a life over decades, the thing you are growing into rather than the mood you are in today. Of the twelve signs, this is the one almost everyone knows about themselves, because unlike the Moon or the ascendant it can be had from a birthday alone.

It can be had from a birthday alone, but not always from a table of dates. Nearly every list of star sign dates prints something like "Leo: 23 July to 22 August", and those boundaries move. The Sun crosses into a new sign at a specific instant, and because a tropical year is about six hours longer than 365 days, that instant drifts by up to a day and a bit across the leap-year cycle. If you were born on the 22nd or 23rd of a month you have a real chance of having been given the wrong sign your whole life - and no fixed table can tell you, because the answer depends on your year, and on your birth time if you were born within a few hours of the change.

A cusp birthday shows how this zodiac Sun sign calculator behaves. Enter 23 July 1990, tick I do not know my birth time, and the result reads Leo at 0°23', with the notice "You were born on a cusp day - the Sun moved from Cancer to Leo. A birth time settles it." Add a birth time of 06:00 and New York as the birth place, and the answer is Leo at 0°18' with no warning. Enter 23 July 1993 instead and the date alone gives Leo at 0°39', since that year the change happened the day before.

This calculator does not use a table. It computes where the Sun was, from the standard solar series in Jean Meeus's Astronomical Algorithms, and reports the result to the arcminute. The positions are checked against JPL Horizons, NASA's own ephemeris service, and agree with it to within four thousandths of a degree. If your birth falls close enough to a boundary that the answer depends on your birth time, the tool says so and shows you both possibilities rather than picking one. Everything runs in your browser - your birth date is never uploaded, logged or stored.