Birth details needed for matching
Matching needs the birth date, the birth time, and the birth place for both people. The Moon's nakshatra, which most matching methods use, changes about every day, so the time matters.
What it is
The Moon's nakshatra changes roughly every 24 hours, and the Moon's sign about every two and a half days. A time error of an hour can change the nakshatra if the birth falls near a boundary.
How it is worked out or read
Use the time from a birth certificate or hospital record where possible. If the time is uncertain, the matching result is uncertain too, and that should be noted.
Where it appears on this site
The chart checks and birth chart tools take the same details. The how to get a birth time article lists sources.
Which details matter most
For matching, the birth date, the birth time and the birth place all matter, and the time matters most because the Moon's nakshatra changes roughly every day. A small error in the time can move the Moon into a neighbouring nakshatra when the birth falls near a boundary, which changes the result. Each person's details should therefore be as exact as the records allow, and the source should be noted.
The place affects the time zone and the local sidereal time, so the latitude and longitude are also needed. Using the wrong place can shift the Moon's position only slightly, but it can still matter near a boundary.
Checking the details before comparing
Before comparing two people, check each person's details independently. Confirm the time zone offset, the coordinates of the place and the ayanamsa used. Compute each Moon position and note the nakshatra and its end time, so that the reader knows how close each birth is to a boundary. A comparison made with unchecked details is likely to be misleading.
Consent and privacy
Details for another person should be used only with that person's agreement, and should not be stored or shared without it. The site keeps no record of the details entered on its tools, and each calculation runs in the browser. Anyone collecting details for a family should keep them private and secure, as they are personal data.
A worked example of boundary sensitivity
Suppose a birth at 08:00 local time falls with the Moon at 13 degrees 15 minutes of a nakshatra that ends at 13 degrees 20 minutes. A forty-minute difference in the time would move the Moon into the next nakshatra. The reader should therefore record the time to the minute, check the nakshatra end time for the date, and note how close the birth is to the boundary before comparing.
Recording sources for each detail
For each person, record where each detail came from: a certificate, a hospital record, a family memory or an estimate. This record helps when a result seems surprising, because it shows which inputs are firm and which are approximate, and it lets the reader decide how much confidence the comparison deserves.