By Jess Kroll | Updated March 24, 2022
The Chinese zodiac is best known for dividing births by year, with the cycle beginning in late January or early February according to the lunar calendar. While it also considers month, day, and hour, the emphasis on month is less pronounced than in other traditions.
In most Western‑influenced countries, the standard system is the tropical zodiac. It divides the year into twelve signs—Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius, and Pisces—each lasting roughly one month and starting around the 21st of each month. The sun’s position at birth determines a person’s sign, but the birth year itself is not factored into personality interpretations.
Hindu, Jyotisa, and Vedic astrology share a similar structure, grouping the year into twelve signs that largely mirror Western equivalents. For instance, Mesha (the ram) corresponds to Aries, Mithuna (the twins) to Gemini, and Dhanus (the bow) to Sagittarius. Differences arise mainly from the observer’s latitude and the slight shift in star positions, leading to minor variations in sign boundaries.
Often used in newspapers and popular horoscopes, the tropic (tropical) zodiac assigns fixed dates to each sign, typically changing on the 21st of each month regardless of the sun’s actual position. This standardized approach simplifies daily forecasts, though it can diverge from the precise celestial positions used in sidereal calculations.
Contrasting the tropical system, sidereal astrology tracks the sun’s real-time movement relative to the fixed stars. Sign boundaries shift mid‑month, usually between the 13th and 16th, and can vary yearly. Scholars and astrologers continue to debate which method more accurately reflects astrological influences.
In January 2011, the possibility of adding a 13th sign—Ophiuchus—between Scorpio and Sagittarius sparked renewed discussion. Some astronomers argue that the Earth’s precession and other celestial mechanics necessitate this adjustment, shortening the duration of each existing sign. Whether to adopt Ophiuchus remains contentious, and its inclusion would affect interpretations for people born between November 29 and December 15, who might be classified as Scorpio, Sagittarius, Ophiuchus, or their sidereal equivalents.
