The sky changes while the clock moves
A birth chart describes one instant. The Moon moves appreciably over a day, while the angle between the eastern horizon and the zodiac changes much faster. That horizon intersection is the ascendant. Its sign determines house one in a whole-sign chart, so an incorrect time can shift every house label.
Even a chart with no saved profile needs an honest time input. A software form that silently inserts 12:00 creates a plausible-looking chart, but plausibility is not evidence that the rising sign is correct.
Exact, approximate, and unknown are different states
An exact time has a source such as a birth record. An approximate time might be “between 8 and 10 in the morning.” Unknown means there is no defensible clock time. These should lead to different outputs. For an approximate range, a system can calculate several instants and show only placements that remain stable throughout the range. For an unknown time, it should suppress the ascendant and houses.
The current Kalika calculation beta accepts exact times only. If your time is approximate or unknown, wait for the uncertainty-aware flow instead of entering an invented time.
Timezone is part of the birth time
A local clock time must be converted to a universal instant. That conversion needs a timezone for the birthplace and the date of birth. Daylight-saving changes can make a clock time ambiguous or impossible. Historical rules can also differ from today’s offset.
Kalika rejects ambiguous or nonexistent local times rather than choosing silently. The calculation details show the resolved UTC instant and offset so that you can compare it with another chart. A city preset is a convenience, not a substitute for checking the place.
What to check if a chart looks wrong
First recheck the date format, AM/PM, city, timezone, and coordinates. Next compare the chosen ayanamsa and node convention. Only after those match should you compare signs and degrees. If a placement is close to a boundary, a small difference can change its label even when the raw astronomical positions are close.