The maths, shown.

Your birth time is converted to Universal Time using the time zone and daylight-saving rules that were in force on your birth date in your birthplace, from the IANA time-zone database. A 1969 birth in Wisconsin, for example, is converted with Central Daylight Time, because that is what the clocks were on.

Planetary positions come from the Swiss Ephemeris, the planetary tables that professional chart software runs on. We use the tropical zodiac and Placidus houses, the defaults most Western astrologers use, so your chart will match theirs.

What is on the chart page

Sun, Moon, Mercury, Venus, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto and the North Node, each with sign, degree and arc-minute, house, and a retrograde mark where it applies. The Ascendant and Midheaven. The twelve house cusps. The ten tightest aspects between those points, with orbs: conjunctions and oppositions within 8°, squares and trines within 7°, sextiles within 4°.

The twelve-month outlook

We scan every day of the coming year for Jupiter, Saturn, Uranus, Neptune and Pluto within one degree of your Sun, Moon, Mercury, Venus, Mars, Jupiter, Saturn, Ascendant and Midheaven, and record the day each pass is closest. Those are the dates printed in the reading. Retrograde loops give several passes, and all of them are listed.

The birth-time note

We recalculate the chart minute by minute either side of the time you gave and find how far it can move before the Rising sign or the house of the Sun or Moon changes. The reading prints that range, so you know exactly which lines to trust.

What we check

The calculation was cross-checked against an independent ephemeris on test charts: positions agreed within a third of an arc-minute. If your chart doesn't match a professional one, the usual cause is the birth time or an ambiguous place; tell us and we'll look.