Prepare birth data without inventing precision

Keep the original details

Write the birth date in an unambiguous format and preserve the local time exactly as you received it. If a document says 2:30, check whether it identifies morning or afternoon rather than assuming. Record where the information came from, such as a document or a family recollection. You do not need to upload an entire identity document to keep a useful source note for yourself.

Keep an estimate as an estimate. If you only know that the birth was in the afternoon, do not convert that into a precise minute because a form expects one. Record the possible interval and leave unresolved questions visible. A polished chart cannot make uncertain input more certain, and a precise-looking label can mislead you when you later compare two readings.

Identify the place and the historical clock

Use the birth city, region and country, not your current address. Cities can share a name, so confirm the intended location before accepting a map result. A real calculation needs the location and an appropriate conversion of local civil time. Keep the original local entry separate from any converted time so that you can see what the service changed and why.

Time-zone and daylight-saving rules have changed historically. The IANA time-zone database records such changes for representative locations, which is why a current UTC offset is not a sufficient assumption for every past birth date. You do not have to perform the conversion yourself, but a chart service should make the interpreted date, location and time clear enough to review.

Use a final input check before any calculation: read the date aloud, confirm the time format and check the location on its own merits. Keep a note if the information was transcribed from handwriting or translated from another record. If you correct a detail later, make a new version of the input summary instead of silently replacing it. This makes it possible to understand why two charts differ without assuming that the interpretation itself has changed or that one result is more personally meaningful.

Decide what can be requested honestly

Before requesting a chart, make a small input summary: date, local time, time confidence, place and source notes. If a detail is missing, state that explicitly. Ask how the output handles it. A service should not silently substitute a guessed time and present all time-dependent features as established. An explanation of what cannot be calculated is part of a useful result.

For a two-person comparison, repeat the same preparation separately for each person and consider their permission before using their details. Avoid treating one person’s uncertain information as equivalent to another’s documented data. Keep the completed record for future reference, but remember that collecting correct input supports reproducible calculations; it does not turn an astrological interpretation into a factual account of a person or relationship.

Sources

• IANA time-zone database
• Swiss Ephemeris documentation