Aries is the astrological Zodiac sign that s the constellation Aries. In the tropical zodiac, Aries is from March 21 to April 20 beginning at the vernal equinox. Under the sidereal zodiac, it is now from April 15 to May 15. The opposite sign to Aries is Libra. The corresponding month in the Babylonian calendar is "Arax Nisânu", which is made for Anu.