No exact birth time? Start with what you know
How to record uncertainty, avoid invented precision and decide whether a detailed chart file is useful to you.
“Around breakfast” is useful information. “08:00 exactly” is a different claim. Preserve the distinction. A chart becomes less useful when a convenient default quietly turns into a fact about your birth.
Write down the evidence first
Record whether the time came from a certificate, a hospital record, a family memory or an estimate. Keep the original wording and any plausible range. A written time is a record, not proof that the clock or recording process was exact.
The Swiss Ephemeris manual describes house calculations using time and geographic coordinates. This is why a house-based reading needs more than a birthday. Sensitivity depends on the particular chart and method; there is no universal “safe number of minutes”.
Ask what changes across the range
If the possible interval is known, compare calculations at several points within it. Mark which placements remain stable and which change. A stable placement is a stable calculation under those inputs, not proof of its astrological meaning.
A useful request: “My time is remembered as between 7 and 9 in the morning. Please distinguish stable chart features from claims that depend on choosing one time.”
Do not manufacture certainty
A noon chart can be a labelled working convention; it must not become your asserted birth time. Likewise, fitting a time to remembered life events produces a hypothesis. Keep the fitted time separate from the recorded one.
Decide before ordering
If most of your questions depend on uncertain houses or fine timing, a detailed file may not be the right purchase yet. Gather records, inspect the sample, and state uncertainty when discussing an order. Do not replace an unknown time with a confident guess just to finish a form.
Read the wider discussion of birth-time sensitivity, keeping in mind that example ranges are not guarantees for every chart.