Birth time
Your birth time fixes the ascendant, the houses and the divisional charts, so it is the most sensitive detail in a Kundli. A few minutes can change the finer charts, while the Moon sign usually stays the same.
Also known as: time of birth, janam samay
The ascendant passes through all twelve signs each day, so each sign rises for only about one and a half to two and a half hours in India, and anywhere from under an hour to nearly three in the UK. The Navamsa ascendant changes roughly every 10–15 minutes and the D60 every two minutes or so. Even dasha dates shift: an hour’s error can move them by several months.
Use the time on the birth certificate or hospital record, in local clock time; many astrologers prefer the moment of the first cry or breath. Older records may be in India’s war time (1942–45) or summer time abroad, and these historical clock changes are allowed for when your Kundli is calculated from the place of birth.
If you do not know your time, the planets’ signs, usually the Moon’s nakshatra and the broad dasha sequence remain useful, but the ascendant and houses do not. A chart cast for 12:00 noon is a placeholder, not a reading. An astrologer can narrow the time through rectification, working back from known life events.