Mercury retrograde 2026–2027

Mercury retrograde is the stretch when Mercury, seen from the Earth, appears to move backwards through the zodiac. Mercury is the planet closest to the Sun and the fastest after the Moon, so it overtakes the Earth often: it turns retrograde three times a year, sometimes four, and stays retrograde for 20 to 24 days each time.

Around each turn it hardly moves. The calendar marks it stationary while it covers less than 8′ of arc a day, the same limit behind the S the app's charts show: for one and a half to four days around each station.

Mercury goes back over nine to sixteen degrees and then crosses them a third time. The pre-shadow begins when Mercury, still moving direct, first reaches the degree where it will turn direct; the post-shadow ends when it regains the degree where it turned retrograde. Counting both, a Mercury retrograde with its shadow covers about eight weeks.

Tradition reads any retrograde planet as going back: a return, a revision, a step taken again. Where the question is about something coming back, that is a good sign; otherwise it shows a matter going the wrong way. Its stations are the weakest moments of all, the planet barely able to act.

William Lilly, in Christian Astrology (1647), counts a retrograde significator against the matter it stands for: discord, contradiction, a running back on what was done, or the business left unfinished. Mercury rules letters, messengers, contracts and trade, so those are the matters its retrograde touches when it is the planet that signifies them.

Each station is solved from the Swiss Ephemeris, built on NASA JPL's DE431: the moment Mercury's geocentric, tropical longitude stops changing, found to the second from the ephemeris itself. The shadow's edges are found the same way, as the moments Mercury stands at the degree of the other station.

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