☉ What planet rules each day of the week? One word a day, and a sentence on Sunday

Every day of the week belongs to one of the seven traditional planets: Monday to the Moon, Tuesday to Mars, Wednesday to Mercury, Thursday to Jupiter, Friday to Venus, Saturday to Saturn and Sunday to the Sun. Umbriel's free Sunday Sentence shows you today's planet and asks for one word. On Sunday your seven words are strung into a sentence, exactly as you typed them.

• What you'll needOne word a day; no chart and no account
• What you getToday's planet and when its day began, a slot for one word, your week's words as one sentence on Sunday, and a printable plate of the year's fifty-two sentences
• CostFree, no account required

The names of the weekdays are an astrology lesson hiding in plain sight. Sunday is the Sun's day and Monday the Moon's. Saturday is Saturn's. The rest came into English through the Norse gods matched to the Roman ones: Tiw for Mars on Tuesday, Woden for Mercury on Wednesday, Thor for Jupiter on Thursday and Frigg for Venus on Friday. In French, Spanish and Italian the planets are still right there: mardi, miércoles, giovedì, viernes.

The order is not arbitrary. It comes from the old sequence of the seven visible planets by speed, Saturn, Jupiter, Mars, the Sun, Venus, Mercury and the Moon, each ruling one hour of the day in turn. Count twenty-four hours on through that sequence and the planet that rules the first hour of the next day is always three steps along the list. That is the week.

The Sunday Sentence gives each day one word. The card shows whose day it is, and, if Umbriel knows roughly where you are, when that planetary day began, because by the old count a planet's day starts at sunrise, not midnight. Before sunrise it says it is still yesterday's planet's day.

You give the day one word. Any word. On Sunday the week's words are strung together in order, Monday to Sunday, into a sentence. Nothing is rewritten: no capital letter added, no full stop, no tidying. A day with no word is simply skipped, with no gap left where it would have been. So someone who only ever opens it on a Sunday can fill in the days they remember and still get their sentence.

Over a year that is fifty-two sentences, printable as one engraved plate. Some will make sense. Many will not, and those are often the best ones.

Your words stay private, on your device, and if you sign in they sync end to end encrypted, the same way the journal does. Nothing is posted.

A day's planet is not read from a table of weekdays. It is the ruler of the first planetary hour, taken from the engine's planetary-hours calculation at noon of that local day, so the local weekday is never confused with the date in Universal Time. The planetary hours run through the Chaldean order, Saturn, Jupiter, Mars, the Sun, Venus, Mercury and the Moon, starting at sunrise with the day's own planet. When a location is known, the card also gives the sunrise that began today's planetary day and, before that sunrise, says that by the old count it is still the previous day's planet. The sentence is assembled from Monday to Sunday by joining the words exactly as stored, one space apart; nothing is capitalised, punctuated or corrected, and a day with no word contributes nothing. Each entry stores the date, the word and the day's planet.