I hate to say that most of you are wrong ... but you are:
1) Equinox and solstices happen exactly at the same moment everywhere on earth, regardless of latitude or longitude. But because we "normalize" time by time zones to the nearest hour, they do not necessarily result in the same durations at each locations (hence the use of nautical almanac and normalization calculations for sunset and sunrise).
2) The local differences in durations are minor. Also, as the equinoxes are "moment" in space, very very seldom do we actually have, anywhere on the planet, a day followed by a night (or vice versa) of exactly 12 hours. Generally what happens for the equinoxes is that, one day is close to 12 hours duration but not quite, either greater or smaller - re: fall or spring, and the very next day is, in reverse, smaller or greater than 12 hours.
3) While for calendar reasons and normalization reasons we humans like things always on the same date (the "21st), in reality, the earth's travel around the sun are not that "steady" and the equinoxes and solstices can fall, from year to year, on different days by 1, 2, 3, and even (but rarely, though it is the case this year) 4 days.
