Of everything you enter into a kundli form, the time of birth carries the most weight — and it is also the number people are least sure about.

The arithmetic

The Earth turns once in roughly 24 hours, so the whole zodiac — 360 degrees — passes the eastern horizon in that time. That works out to 15 degrees an hour, one degree every four minutes.

The point rising on the eastern horizon at your birth is the lagna, the ascendant. It is the first house of your chart and everything else is counted from it. Four minutes moves it a degree; two hours, on average, moves it into the next sign entirely.

What is affected and what is not

Not everything is equally sensitive, and knowing which is which tells you how much to worry.

  • Very sensitive: the ascendant, the house positions of all nine grahas, and every divisional chart. The D60, which divides each sign into sixty parts, changes every two minutes.
  • Moderately sensitive: the Moon's nakshatra and therefore the starting point of the Vimshottari dasha. The Moon moves about half a degree an hour.
  • Barely sensitive: the signs of the Sun, Jupiter, Saturn, Rahu and Ketu. Saturn takes two and a half years to cross a sign; a few hours changes nothing.

If you do not know the exact time

Most people in India born before the 1990s do not have a recorded birth time, and there is no shame in that. A few practical steps:

  • Check the birth certificate and the hospital discharge summary. Both often carry a time that nobody in the family remembers being recorded.
  • If the family remembers only "morning" or "after dinner", use the middle of that window and treat the ascendant as provisional.
  • The Moon sign and the dasha sequence remain usable even with a rough time, as long as the uncertainty is under a couple of hours. Read those and hold the house positions lightly.

What we do not do

There is a practice called birth-time rectification, which works backwards from life events to guess a precise time. We do not offer it. Done honestly it takes an experienced astrologer many hours with the person; done automatically it is fitting a curve to a handful of remembered dates, and it produces a confident-looking time that is no more accurate than the guess you started with.

The practical answer

Enter the best time you have and note how sure you are. A chart from a time you trust to the minute can be read closely. A chart from a time you trust to the hour should be read for its Moon and its dashas, and its house placements taken as a sketch.