Historical timezone uncertainty
How to represent dates for which political rules, local mean time, clock adoption, or the original record are uncertain.
Calculation contract · released 2026-08-18
Definition
Historical civil time is reconstructed evidence, not a timeless mapping. A database rule can be precise while the underlying historical record remains uncertain.
Calculation procedure
Retain the source wording, jurisdiction, assumed clock regime, tzdb result, competing interpretations, and a bounded instant interval; recompute sensitive chart features across that interval.
Required inputs
- Original timestamp evidence
- Location and jurisdiction
- Candidate civil-time rules
- Confidence or interval policy
Maha convention
Maha separates timezone-rule confidence from event-time confidence and refuses to print unstable houses as exact facts.
Uncertainty and edge cases
Pre-standard-time records and date-only corporate filings may have uncertainty measured in hours or a full day, not seconds.
What this does not establish
Modern software precision cannot recover information absent from the historical record.
Authoritative references
These sources establish the calculation vocabulary, data product, or transformation convention. They do not establish astrological interpretation.
- Time Zone Database
Internet Assigned Numbers Authority · 2026c
Versioned civil-time-zone identifiers, UTC offsets, daylight-saving transitions, and historical rules for representative locations.
Boundary: The database records civil-time practice and can contain historical uncertainty; it does not supply leap seconds or astronomical time scales.