Sun sign versus moon sign
Almost every free tool, this one included, gives you a sun sign. It is worth knowing exactly what that covers, what it does not, and why the follow-up question needs information a birth date cannot supply.
By Jamey Weber, editor and developer at FusionStudios. Last reviewed .
Three placements, three different clocks
| Placement | Tracks | Changes sign roughly every | You need |
|---|---|---|---|
| Sun sign | Position of the sun | 30 days | Birth date |
| Moon sign | Position of the moon | 2 to 3 days | Birth date and time |
| Rising sign | Sign on the eastern horizon | 2 hours | Birth date, time and place |
Why the sun sign is the one everyone knows
Because it is the only one a newspaper column could use. A sun sign needs nothing but a date, which means it can be printed as twelve paragraphs and read by anyone. The moon sign needs a birth time, which most people do not know precisely, and the rising sign needs a place as well. The popularity of the sun sign is a fact about what is easy to publish, not about which placement anyone considers most important.
The honest limit of this site
Birthdex takes a month and a day and returns a sun sign, a birthstone and a birth flower. All three of those depend only on the calendar, which is exactly why the whole thing can run in your browser without your birth date ever leaving your device. The moment a tool asks for your birth time and location, it is collecting something quite different, and usually sending it somewhere. That is a trade worth noticing.
There is one place where even the sun sign runs out of certainty: birthdays on a sign boundary. Those need a birth year, and sometimes a time, to settle. The cusp guide sets out every boundary date and explains why.
Where to go next
If you want your sun sign and the traditions attached to your birth month, the birth profile tool does that in one step, and the sign pages give the dates, element and modality behind each one. If you want a moon or rising sign, you need a chart calculator that asks for your birth time. We do not build one, because doing it properly means giving up the privacy promise that makes this site worth using.
Frequently asked questions
What is a sun sign?
It is the zodiac sign the sun was in on the day you were born. It is the sign meant when someone asks what your star sign is, and it is the only one that a birth date alone is enough to work out.
What is a moon sign?
It is the sign the moon was in at the moment of your birth. The moon moves through all twelve signs in roughly a month, spending around two and a half days in each, so it changes far faster than the sun and needs a birth time to pin down.
Can Birthdex tell me my moon sign?
No, and it does not pretend to. This site works from a date, and a date is not enough. Working out a moon sign needs the time and place of birth checked against an ephemeris.
What is a rising sign?
The rising sign, or ascendant, is the sign that was coming up over the eastern horizon at the moment of birth. It changes roughly every two hours, so it is the most time-sensitive of the three and the one most often wrong when a birth time is approximate.
Sources and limits
This guide describes how the three placements are defined within Western astrology. It is an explanation of a convention, not a claim that the convention predicts anything. No source here supports, and this site does not make, any claim about personality, health or the course of anyone's life.
Keep reading
Every guide is listed on the guides hub. How the reference data on this site is put together, and where it comes from, is on the methodology page.