Sun Signs:
Astrolonomical vs. Astrological

Astrologers today are working with a dating scheme that has been outdated for over two millenia--and which was never particularly accurate to begin with. The traditional dates for the positions of the Zodiac constellations are simply incorrect. But modern astrologers don't actually observe the sky the way ancient astrologers did. They simply go by ancient charts based on the position of the Sun in the stars over 2000 years ago.

As the following table indicates, the traditional dates for the Sun's position in the Zodiac are not only out of sync with the actual sky, but they are artificially separated into 30-degree segments to make each sign last an average of 30 days. As you can see in the right side of the table, the signs are anything but evenly distributed across the sky. You will also notice that there is in fact a thirteenth constellation--Ophiuchus--which is ignored by traditional Astrology.

TODAY (c. 2000 C.E.)
ConstellationDate SpanDays ConstellationDate SpanDays
Aries21 Mar - 19 Apr30 Aries 19 Apr - 13 May25
Taurus20 Apr - 20 May31 Taurus 14 May - 19 Jun37
Gemini21 May - 20 Jun31 Gemini 20 Jun - 20 Jul31
Cancer21 Jun - 22 Jul32 Cancer 21 Jul - 9 Aug20
Leo23 Jul - 22 Aug31 Leo 10 Aug - 15 Sep37
Virgo23 Aug - 22 Sep31 Virgo 16 Sep - 30 Oct45
Libra23 Sep - 22 Oct30 Libra 31 Oct - 22 Nov23
Scorpio23 Oct - 21 Nov30 Scorpius 23 Nov - 29 Nov7
    Ophiuchus 30 Nov - 17 Dec18
Sagittarius22 Nov - 21 Dec30 Sagittarius 18 Dec - 18 Jan32
Capricorn22 Dec - 19 Jan29 Capricornus 19 Jan - 15 Feb28
Aquarius20 Jan - 18 Feb30 Aquarius 16 Feb - 3/1124-25
Pisces19 Feb - 20 Mar30-31 Pisces 12 Mar - 18 Apr38

For a graphical illustration of the sun's different position in the sky, see this comparison of the Sun's position over the last 4000 years.

For a more information and a fuller explanation, see What's Your Sign?, by Philip Plait , an Astronomer at Goddard Space Flight Center, and The Real Constellations of the Zodiac, by Lee Shapiro, director of the Morehead Planetarium.