1 of 12 · March 21 – April 19 · Fire · Cardinal
Aries opens the tropical year at the spring equinox, which is why it is given the leading role. The ram charges rather than negotiates, so the sign is associated with first moves, with starting things badly and with recovering from it anyway.
The dates above are the conventional ones and hold for most years. The Sun actually crosses into Aries at a slightly different moment each year — by up to a day — so a birth on March 21 or the day before can land on either side depending on the year and the hour.
If the birthday is on that edge, check it with the zodiac lookup using the exact time and place rather than a printed range.