What a birth sky is, and how to read the picture

You have probably heard your sun sign. Fewer people have seen the actual sky that stood over them on the day they were born. That picture is what we call a birth sky, and it is one of our favorite things to show.

Why the same birthday does not mean the same sky

The sky depends on three things: the date, the time and the place. Two people born on the same date in different cities, or at different hours, looked up at a different arrangement. The Moon moves quickly, about a sign every two and a half days, so the time of day can matter a lot. That is why we ask for a birth time, and why we say so when you do not have one. Without a time we show the evening sky of that date.

What the picture shows

The picture is a map of the heavens above one spot. You will see:

• The Sun and the Moon, including the Moon's phase on that day.
• The planets that were above the horizon.
• The brighter stars, placed from real star catalogs.

The positions are calculated, not drawn by hand. We use an open astronomy library to work out exactly where each body was, then draw it in the right place.

Finding your way around

North is always at the top of our map, and east is on the left. That is how star charts are drawn, and it surprises people at first, because a map of the ground has east on the right. The reason is that you are looking up, not down.

The little hat at the center marks the spot straight above you. Choose a direction under the picture and the hat turns to point that way, so you can hold the picture up to the real sky and match what you see.

What it means

Whatever you take from it is for you. Some people enjoy the symbolism of their sun and moon signs. Others simply like seeing the real sky from a moment that mattered. We offer it for reflection and fun, and we are careful never to present it as a prediction.

Try it with a date that matters to you: open the Sky in the app. If you would like to see where the Moon will be this month, our Moon calendar lists every new and full moon.

For entertainment and reflection only. Nothing here is a prediction or advice.