Birth time calculator
If you already know your exact birth time, you do not need this page. Put the time straight into the kundli calculator and read the chart. This one is for the stage before that: you have a rough idea, an hour or a morning or nothing at all, and you want to know how much that gap actually costs you.
What the number means
Every distinct chart in your window is a different reading. Not a slightly different one: a different lagna moves every house, and a different navamsa changes the chart most astrologers read for marriage. When a window allows seven charts, six of those readings are about somebody who is not you.
The surprise for most people is that the ascendant is the forgiving part. It holds for about two hours at a stretch, so a one hour window often shows a single lagna and looks harmless. The navamsa underneath it has usually moved several times in the same hour.
Why it cannot tell you the time itself
Nothing that knows only your date and your birthplace can. Those fix where the planets were, and the ascendant follows from the clock, so with the clock unknown every time in your window remains equally possible. The calculator can only report the size of the question.
Answering it needs evidence from outside the chart, and the evidence is your own life. Dated events leave a signature: build the chart for each possible time, score each one against what actually happened and when, and the times that fit stay standing. The method is written up here, including what it will not claim.
Before you rely on any of this, look for the record
A birth time somebody wrote down on the day beats a reconstructed one every time. Hospital registers, the original entry in the municipal register rather than the printed certificate, a janma kundli cast when you were an infant. The full order of places to look is here, and it is worth an afternoon before you settle for a window. If nobody remembers and nothing was written down, that is the ordinary case and it is workable.
Takes about 10 minutes.
Birth time calculator, answered
What does this calculator actually work out?
It takes the range your birth time could fall in and scans it, then reports how many distinct charts that range still allows, which ascendant signs it covers, and the clock times where the lagna changes from one sign to the next. It does not draw a kundli, because a kundli needs one time rather than a range.
How is this different from a kundli calculator?
A kundli calculator needs an exact birth time and draws the chart for it. This one is for the stage before that, when you do not have an exact time and want to know whether the gap matters. If you already know your time, use the kundli calculator instead.
My window shows one lagna but several charts. What does that mean?
It means your ascendant sign is settled but your navamsa is not. The D9 changes about every thirteen minutes, so an hour of uncertainty can hold one lagna and half a dozen navamsa signs. Since the navamsa is the chart most often read for marriage, this is usually the part people care about.
Can this give me my birth time?
No, and nothing that only knows your date and place can. It tells you how wide the question is. Narrowing it needs evidence, which means dated events from your life scored against each possible time.
How precise are the times it reports?
The window is sampled once a minute, so a reported change time is accurate to about a minute. That is finer than the uncertainty anyone arrives with, so it is not the limiting factor in practice.