Converting local civil time to UTC
Why a local date and clock reading require a named timezone, historical rule set, and ambiguity policy before chart calculation.
Calculation contract · released 2026-08-18
Definition
A local civil timestamp is a wall-clock label. It becomes a unique instant only after a timezone rule supplies an offset and any fold or gap is resolved.
Calculation procedure
Parse the stated local date and time in the named IANA zone, resolve transition ambiguity explicitly, retain the selected UTC offset, and serialize the resulting instant in UTC.
Required inputs
- Local calendar date
- Local clock time
- IANA timezone identifier
- Timezone database version
- Fold or gap resolution when applicable
Maha convention
Maha retains local time, IANA zone, resolved offset, tzdb version, fold choice, and the resulting UTC instant as one provenance unit.
Uncertainty and edge cases
If the historical timezone rule or original record is uncertain, the system must retain an interval or confidence classification rather than inventing minute precision.
What this does not establish
A precise UTC conversion does not make the source birth or event time accurate.
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.
- RFC 3339: Date and Time on the Internet
Internet Engineering Task Force · RFC 3339, July 2002
A machine-readable timestamp profile with explicit offsets and a UTC designator.
Boundary: A serialized offset does not identify the civil-time rules or timezone database version that produced it.
- SPICE Time Subsystem
NASA/JPL Navigation and Ancillary Information Facility · 2021-12-31 revision
UTC, TAI, TT, TDB, calendar and Julian-date representations, leap-second kernels, and conversions used by SPICE.
Boundary: A civil timestamp is not an ephemeris time until its zone, offset, ambiguity resolution, leap-second data, and target time scale are declared.