Don't know your birth time? What your chart can still tell you

That is far more than most people expect. The planets move slowly enough that a whole day barely shifts them, so the core of your character is already there on the page. You can calculate your birth chart without a time right now and see exactly which parts are fixed and which are waiting.

Every planet's sign is worked out from real astronomical data for your birth date, and for almost everyone, the sign does not change across the day.

• Your Sun. The Sun moves about one degree a day, so your sun sign is certain unless you were born on the day it changed sign. If you were, the calculator will tell you which sign it sat in at noon, and you can read both neighbouring signs to see which fits.
• Mercury, Venus and Mars. These personal planets shape how you think, love and fight. They move slowly enough that your birth date settles them.
• Jupiter, Saturn, Uranus, Neptune and Pluto. These hold the same sign for months or years. They are certain.
• Most aspects. The angles between planets, the squares, trines and oppositions, barely move in a day. A Venus square Mars is still a Venus square Mars, and that tells you a great deal about your love life.

Put together, that is a solid portrait. You can read how you communicate, what you find attractive, how you handle anger, where you are lucky and where life asks you to work hard.

Three things need the exact time and place.

Your rising sign. The ascendant is the sign coming up over the eastern horizon at the moment you were born. The horizon turns a full circle every day, so the rising sign changes roughly every two hours. Without a time it could be any of the twelve.

Your houses. The houses are measured from the rising sign, so they go with it. Without them you know that your Venus is in Libra, but not whether that love of beauty plays out at work, at home or among friends. Our guide to the twelve houses explains what each one rules.

The exact degree of your Moon. The Moon is the fast mover. It travels about thirteen degrees a day, so across one day it can shift by half a sign, and sometimes changes sign altogether.

When you leave the time blank, the calculator places your birth at noon. Noon sits in the middle of the day, so no planet can be more than half a day away from where it really was. That keeps the error as small as it can be, especially for the Moon.

Then it is honest about what noon cannot give you. The rising sign, the houses and the exact Moon degree are hidden, and the wheel shows those parts hatched, so you can see at a glance what is solid and what is unknown. Nothing is invented to fill the gap.

Often, yes. If your Moon was in the middle of a sign at noon, it was very likely in that sign all day, and you can read your Moon sign with confidence.

If the noon Moon sits near the start or end of a sign, the picture changes. It may have crossed into the next sign earlier or later that day. In that case, read both Moon signs and ask which one describes how you behave when you are tired, upset or at home. People nearly always recognise their Moon. A Moon in Leo wants to be seen when it is hurt; a Moon in Virgo wants to tidy something.

The same care applies when you compare charts. In zodiac compatibility, a Moon aspect that sits near the edge of its orb is marked uncertain when a birth time is missing, so you know which links are firm.

Your time is probably written down somewhere. Try these, roughly in order.

• Ask family. A parent, grandparent or older sibling may remember. Ask what was happening: "Was it before breakfast? Had the news come on?" A scene is easier to recall than a number.
• Check your birth certificate. In some countries, and for twins and multiple births in others, the time is recorded on the certificate itself.
• Look for hospital or maternity notes. Records from the birth often include the time. Your family may have kept a red book, a card, or a letter from the hospital.
• Search the baby book and old cards. Announcements, keepsake bracelets and baby books often record the time to the minute.
• Ask the register office or hospital records department. Some will search their archives on request.

Even a rough time helps. "Early morning" narrows your rising sign to a handful of options, and you can read those few to see which one matches how strangers describe you.

Your chart without a time is a portrait without a frame. Start with the Sun, Moon and personal planets, and the aspects between them.

Ask three questions. What does my Sun sign want? What does my Moon sign need? How do Mercury, Venus and Mars go about getting it? Answer those, and you have a working description of yourself that is accurate whether you were born at dawn or at midnight.

Then pay attention to the aspects. A tight square between your Sun and Saturn will shape your life far more than which house it falls in. Tight aspects are the strongest signal in any chart, and they survive a missing time.

When you do find your time, add it. The rising sign and houses will slot in, and the chart you already know will gain its setting. Look up your rising sign and see whether it matches the first impression you give.

Enter your date and place, leave the time blank if you need to, and see what is already certain. Calculate your birth chart, then come back and add your time the moment you track it down.