Planet retrograde calendar

Give it a year and you get every retrograde period that touches it, planet by planet: the day each one turns back, the day it goes direct again, and how long it lasts. Take the table away as a file, or subscribe to it so the dates land in your own calendar. Free, no account, nothing stored.

What it does, and why it is here

“Is Mercury retrograde right now?” is asked far more often than it is answered properly. Most pages give one planet, for the current year, as prose — and quietly disagree with each other by a day, because a retrograde period does not begin at midnight. It begins at a station: the instant a planet’s apparent motion stops and reverses, which falls at some particular hour, and which has to be solved for rather than looked up.

So this page computes the stations from the ephemeris and gives you all eight planets at once, for whichever year you ask. Mercury through Pluto, station retrograde to station direct, with the length of each period.

The other thing it does is get out of the way. This is not a reading and it asks nothing about you — no birth date, no chart, no account. The answer is the same for everybody on Earth, which is exactly what makes the address worth sharing and the calendar worth subscribing to.

What you fill in

• Year — a civil year, and that is the whole form. The current year is already filled in.

A visitor gets this year and the next. The computation itself covers 1550 to 2650, on the DE440 ephemerides.

What you get back

• Station to station — one row per period: the planet, the instant it stations retrograde, the instant it stations direct, and the number of days between the two.
• The periods that straddle the year, included on purpose. One that began last December or ends next January is listed too, because the question is never “which periods started this year” — it is whether a planet is retrograde on a given day.
• The table as a file, to open in a spreadsheet or drop into something else.
• The year as a calendar — download it, or subscribe, and each period arrives as an event in the calendar you already look at. That is the difference between knowing the dates and being reminded of them.
• A shareable address — the year travels in the link, so a message saying “here is 2027” opens on 2027 rather than on today.

Every instant is given in UTC, because a station is one moment for the whole planet and UTC is the only way to state it without ambiguity.

What it does not do

It does not interpret. There is no paragraph on what to avoid signing while Mercury is retrograde, and no advice attached to any period — the dates are the answer, and what you make of them is yours.

It knows nothing about you. No birth chart, no houses, no personal transits: this is the sky’s calendar, identical for everyone, not a reading.

And it lists the eight planets that have retrograde periods. The Sun and Moon never do — the effect comes from the Earth’s own motion past another orbit, and neither of those is an orbit we overtake.

How often each planet turns back, and for how long

Roughly, and it is the shape rather than the exact figure that is worth carrying: the further out the planet, the more of the year it spends retrograde.

Which produces a fact people find surprising: the outer planets are retrograde more often than not. Pluto spends roughly five months and a half of every year moving backwards against the stars, so “Pluto is retrograde” is close to the ordinary state of affairs rather than an event.

Questions

Is it free?

Yes. No account, no e-mail, no limit — and the year you type is used to answer and then forgotten.

Is Mercury retrograde right now?

Ask for this year and read the Mercury rows: if today falls between a station retrograde and the station direct that follows it, then yes. There are usually three or four such windows a year, about three weeks each.

Which years can I ask for?

This year and the next are served without an account. The underlying computation covers 1550 to 2650.

Why are the times in UTC?

Because a station is a single instant for the entire planet. Giving it in one local time would make it wrong everywhere else; UTC is the form that is true everywhere and converts cleanly.

Why is a period from last year in my list?

Because it is still running into this one. What matters is whether a planet is retrograde on a given day, not which calendar year the period happened to start in.

Why are the Sun and the Moon not listed?

They never appear to go backwards. Retrograde motion is what you see when the Earth overtakes an outer planet, or is overtaken by an inner one — and neither the Sun nor the Moon is in that relationship with us.

Do the planets actually move backwards?

No. It is a trick of perspective, the same one that makes a slower car seem to slide backwards as you pass it. The planet keeps going the way it always did; we move past it, and its apparent path against the background stars reverses for a while.

Can I put these dates in my calendar?

Yes — that is what the calendar output is for. Download it once, or subscribe to it and let the periods appear alongside everything else you keep track of.

My dates differ from another site by a day.

Almost always a time zone. A station that falls at 01:40 UTC is still the previous evening in the Americas, so two sites can print different days and both be right. The instants here are UTC and stated as such.

Sources and further reading

• Apparent retrograde motion — why a planet seems to reverse.
• JPL DE440 — the planetary ephemerides the stations are solved from.
• UTC — the scale the instants are given in.