At the equinox, the sun's disk crosses the horizon directly in the east at dawn and crosses directly in the west at dusk. However, because of refraction the sun will usually appear slightly above the horizon when its "true" middle is rising or setting. For viewers at the north or south poles, the sun moves steadily just above the horizon, not obviously rising or sinking apart from the movement in "declination" (and hence elevation) of a little under a half (0.39) degree per day.
The equinox can be as early as March 19 or as late as March 21, the precise time being about 5 hours 49 minutes later in a common year, and about 18 hours 11 minutes earlier in a leap year, than in the previous year. It is the balance of common years and leap years that keeps the calendar date of the equinox from drifting more than a day from March 20 each year.