Mercury stations retrograde on April 4, 1991 at 29° Aries, and direct on April 28 at 17° Aries — 24 days. From the Earth, Mercury seems to back up against the stars as we overtake it, as a car passed on the highway seems to slide backward. Astrology holds it a time for crossed wires and delays. Computed from JPL's approximate orbits; the stations agree with an almanac's to within minutes.