What the Moon sign is
The Moon sign is the zodiac sign the Moon occupied when you were born. Where the Sun sign describes how you grow into yourself, the Moon describes how you recover: your moods, instincts, and the kind of care that actually lands. Many people find their Moon sign more recognizable than their Sun sign, especially at home or under stress.
Do you need a birth time?
Often not. The Moon spends about two and a half days in each sign, so on most days your date and place are enough. On the days it changes sign, the time decides it. This calculator checks the whole local day. If the Moon changed sign on your birthday and you don't know your time, it tells you so instead of picking one, and shows the sign with a question mark.
How it's calculated
The Moon's position is calculated geocentrically, in the tropical zodiac, from a local astronomy library that is checked against published reference charts. The tropical zodiac is measured from the March equinox. It's the zodiac most Western astrology uses. Vedic astrology uses a different, sidereal zodiac, so a Vedic Moon sign is often one sign earlier.
Reading your Moon with your Sun
The Moon is rarely read alone. When your Sun and Moon share an element, what you show and what you need tend to agree. When they don't, you may feel pulled between the life that looks right and the life that feels safe. Your free birth chart shows both, along with how they connect.