TIME, DATE AND PLACE

To calculate a chart, all you need is your time, date, and place of birth. It is possible to cast a chart by hand using an ephemeris and a table of houses, but most astrologers take the shortcut and use astrological software.

Your time of birth 

Most of us know our date of birth, but the more accurate you can be about your time of birth, the better. The MC and IC move through each zodiac sign in exactly two hours and the Ascendant and Descendant take an average of two hours through each sign, so they are moving relatively quickly and a discrepancy of even just an hour can change the picture of a chart quite significantly.

If you do not know your time of birth at all, it is not possible to set up the full horoscope. You will only be able to cast a "flat" chart in which the four angles will be absent and also the house cusps, missing out a great deal of basic information. The Moon’s position will also be in question, since the Moon moves an average of 13° 11´ through the zodiac each day.

So it is worth making every effort to find out. The time of birth is recorded on the birth certificate in some countries but not in others, and some countries offer a “long form” of birth certificate, which includes the time of birth. It is also possible that the hospital may record birth times. Family records and baby books are also helpful. In the absence of written evidence, family members can often be a godsend, perhaps remembering that you were born “around teatime” or “in the evening”, which gives you a starting point. If you have no record at all, some professional astrologers will “rectify” a chart – this is a skilled process of matching significant dates and events in your life to astrological significators in order to arrive at a suggested time of birth.

Your place of birth

Regarding location, it is helpful to be as accurate as possible, although if you were born in a rural area then the nearest town should be sufficient to use as your birth place. If you were born in a city, astrological software usually lists different city districts and suburbs, to create the most accurate chart. If there is no town nearby, it is possible to use just the coordinates for the place you were born.

THE IMPORTANCE OF TIME

An accurate time of birth gives the most accurate chart. With no birth time, we cannot calculate the angles and house cusps.

A DIFFERENCE OF 15 MINUTES

Twins will have very similar charts but often with a few quite significant differences. These are charts for twins born 15 minutes apart.

Birth chart with known time of birth 

This reveals the four angles and the house positions of the planets.

Twin one

Both twins have Aquarius MC, but twin one has a Taurus Ascendant, a 12th-house Sun, and an 11th-house Moon.