A daily horoscope is an astrological forecast for a 24-hour period, calculated by reading the Moon's transit through the zodiac, the position of the Sun, and the active aspects between planets. The Moon moves through one full zodiac sign roughly every 2.25 days, which is why your daily horoscope tone shifts noticeably every two to three days. Each sign carries a ruling planet — Mars for Aries, Venus for Taurus and Libra, Mercury for Gemini and Virgo, the Moon for Cancer, the Sun for Leo, Mars (or Pluto) for Scorpio, Jupiter for Sagittarius and Pisces, Saturn for Capricorn and Aquarius. The strength and aspect of your ruling planet on any given day shapes the tone of your daily forecast.