At one time the constellations and the zodiac signs were aligned. The summer solstice was in the constellation and the zodiac sign of Cancer. The winter solstice was in the constellation and the zodiac sign of Capricorn. But the universe isn’t stagnant. It moves, and the constellations moved, as well. Eventually this created a discrepancy between the constellations and the signs.
The zodiac, unlike the constellations, is static. It never changes. The first day of spring, when the Sun reaches 0° of Aries, will always be 0° of Aries and the first day of spring. The actual time may vary by a few hours, but what is important is that the first day of spring occurs when the Sun reaches 0° of the zodiac sign Aries, not when it reaches the constellation of Aries.
This guide uses the signs for all activities.