Retrograde planets in 1978

Why do planets seem to move backward?

Every planet orbits the Sun in the same direction, and none of them ever reverses. Retrograde motion is a matter of perspective: we watch the sky from a moving platform. When Earth, on its faster inside track, overtakes Mars, Jupiter or any planet farther out, that planet appears to slip backward against the background stars for a while, much as a slower car seems to roll back when you pass it on a motorway. Mercury and Venus work the other way round. They orbit inside Earth's path and move faster than we do, so they appear to reverse when they swing around the near side of their orbit and pass between Earth and the Sun.

That difference splits the retrogrades into two families. Inner planets (Mercury, Venus) go retrograde around their inferior conjunction, close to the Sun in the sky, so they are hard or impossible to see at that time. Outer planets (Mars through Pluto) go retrograde in the part of the sky opposite the Sun, around their opposition, when they rise at sunset and are visible all night.

How often each planet does it

• Mercury: three or four times a year, about three weeks each time.
• Venus: about every 19 months, for roughly six weeks.
• Mars: about every 26 months, for roughly two to two and a half months.
• Jupiter: once a year, for about four months.
• Saturn, Uranus, Neptune, Pluto: once a year, for roughly four and a half to five and a half months; the farther the planet, the longer the stay.

The calendar also includes Chiron, which turns retrograde once a year for about five months.

How the calendar is calculated

The site computes every planet's geocentric, tropical position with its own astronomical calculation engine and tracks its daily speed in ecliptic longitude. A retrograde station is the moment that speed changes from positive to negative; the direct station is the moment it turns positive again. These moments are first located by a coarse scan and then narrowed down by bisection to a fraction of a second, so the station times you see are not rounded to the day.

For each retrograde the calendar also finds the shadow: the pre-shadow starts when the planet first reaches the degree where it will later turn direct, and the post-shadow ends when it gets back to the degree where it turned retrograde. All times are calculated in UTC and displayed in the time zone you pick on the page, so a station that falls late at night in one country can land on the next calendar day in another.

How to read the timeline

Each row on the timeline is one planet, and each bar is one retrograde. The solid part is the retrograde itself; the lighter extensions on either side are the pre- and post-shadow. Long bars stacking up in the lower rows show how the slow planets overlap for months, while the short, repeated marks of Mercury show its rhythm through the year.

A practical way to use it: first look for periods when a fast planet (Mercury, Venus or Mars) is retrograde, because those are the ones most often felt in day-to-day plans. Then check where several bars overlap. A stretch with five or six planets retrograde at the same time is not unusual, especially when the outer planets' retrogrades cluster; astrologers read such stretches as a collective slowdown rather than a single dramatic event. Finally, open the planet's own page to see the exact degrees and the sign meanings involved.