"OMG, I thought I was a Libra all these years - but I'm actually a Virgo!"
Whether you're a subscriber or a cynic, most people are familiar with their star sign. A staggering 75% of us here in the UK read our horoscopes on a regular basis, and 25% of us believe in astrology.
So it's surprising to think that the signs many of us rely on for an understanding of our personality traits - or even the state of our love lives - are likely wrong, and out of sync by nearly one full month.
A piece on BBC iWonder has been doing the rounds on Twitter this week, by pointing out that a massive 86% of us were actually born under a different constellation to our star sign, based on how the sky exists today.
The date that fixes our star sign corresponds to the position of the Sun relative to constellations of stars appearing behind the Sun on our birth date.
The position of the Sun as it’s perceived from the revolving Earth passes through the constellations that formed the zodiac - Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius and Pisces. Zodiac signs were originally determined by which constellation the Sun was "in" on the day we were born.
But in the more than 3000 years since our zodiac system was invented, constellations have drifted and the sky has changed.
So when we consider ourselves to be a well-balanced Libra, or a headstrong Aries, that might not actually be the case.
While it's a widely known fact that traditional signs do not correspond with today's zodiac boundaries, it still comes as a surprise to hear how dramatically they've changed.
The below graph gives a more accurate idea what your real star sign may be, according to boundaries of a specific zodiac constellation defined in 1930 by the International Astronomical Union. It was published online by a Cambridge academic, who notes that the dates can vary by as much as two days from year to year, depending on the cycle of leap years.
The blue "solar zodiac column" indicates the actual dates when the Sun is located within the boundaries of the named constellation (as opposed to where it was when the zodiac system was fixed thousands of years ago):
Click to enlarge:
Graph courtesy of ast.cam.ac.uk
If your birth date falls on the boundary of a star sign and you're not sure which one you really are, the article suggests using the rather brilliant and free software Stellarium to access a precise sky chart of your birthday.
As you can see the graph also contains a 13th star, Ophiuchus, which was left out of the original zodiac.
It's not known why this star - known as the "serpent bearer" - was omitted from the system that was invented thousands of years ago. The Sun clearly passes in front of it after passing Scorpius and before reaching Sagittarius.
The BBC speculates that ancient astrologers perhaps wanted to chart the 360 degree path of the Sun in a mathematically pleasing way of 12 equal parts, each one of 30 degrees.
Whatever the reason, the upshot is that those born in the first half of December actually have a new star sign, Ophiuchus. Depicted as a man handling a serpent, this sign attracts good luck and apparently denotes people who seek peace and harmony, along with those who hold lofty ideals.
According to Live Science, a phenomenon called precession has altered the position of the constellations we see today.
"Unbeknownst to the ancient astrologers, the Earth continually wobbles around its axis in a 25,800-year cycle," it says. "This wobble - called precession - is caused by the gravitational attraction of the Moon on Earth's equatorial bulge.
"Over the past two-and-a-half millennia, this wobble has caused the intersection point between the celestial equator and the ecliptic to move west along the ecliptic by 36 degrees, or almost exactly one-tenth of the way around. This means that the signs have slipped one-tenth - or almost one whole month - of the way around the sky to the west, relative to the stars beyond."
Watch the below video to find out more about the science behind why your star sign might be wrong.