How to find an accurate birth time
An accurate birth time is the most important input for a Lagna-based chart. The best source is a record made at or near the time of birth.
What it is
Sources in order of reliability are a birth certificate or hospital record, a horoscope written by a practitioner soon after birth, a family record or memory, and an estimate. Each lower source should be treated as less exact.
How it is worked out or read
If you have only an estimate, note it when you use the tools, and read the house-based results as approximate. The rectification article explains how a time can be narrowed down.
Where it appears on this site
Enter the time in the birth chart tool in local time. The birth certificate article says what to look for on the record.
Start with documents
The most reliable birth times come from records made at the time. Look first for the hospital's delivery record, the discharge summary or a nursing home register; then for a horoscope drawn up soon after birth by a family astrologer, which often records the time precisely; then for letters, diaries or telegrams sent to relatives announcing the birth. Municipal birth certificates in India often record only the date, so they are useful for confirming the date and place rather than the time.
Asking family members
When no document survives, ask the people who were present, especially the mother, and ask more than one person if possible. Useful questions are about events around the birth rather than the clock alone: whether it was before or after a meal, a prayer time, sunrise or a train's arrival, whether lamps were lit, which shift the doctor was on. Such anchors often narrow the time more reliably than a remembered hour, which tends to be rounded.
Recording the uncertainty
Write down the time you settle on together with its source and its likely range, for example 'about 7:30 am, mother's memory, probably between 7:15 and 7:45'. This note is as important as the time itself. It tells anyone reading the chart later how much weight the Lagna and houses can bear. A time known to the minute supports detailed work with the divisional charts; a time known to the half hour supports the Moon sign and planets but leaves the Lagna open if it is near a sign boundary.
Checking the Lagna's sensitivity
Once you have a range, make charts for its two ends using the birth chart tool. If the Lagna and the Moon's nakshatra are the same at both ends, the uncertainty does not affect the main features of the chart. If the Lagna changes sign within the range, note both possibilities and avoid relying on house-based readings until more evidence is found.
When the time cannot be found
Many people do not know their birth time, and this is nothing unusual. A chart for noon on the birth date gives the planets' signs and, on most days, the Moon's sign correctly; a reading can be built on those. Rectification, estimating the time from life events, is sometimes attempted, but it depends heavily on method and judgement, and its results should be treated as tentative.