Daylight-saving folds: one clock time, two instants
How Maha handles repeated local times when clocks move backward and the same wall-clock label occurs twice.
Calculation contract · released 2026-08-18
Definition
A fold is a backward offset transition that maps two distinct UTC instants to the same local date and clock time.
Calculation procedure
Detect both valid offsets, require an earlier-offset or later-offset choice, calculate both candidate instants when the source cannot distinguish them, and test chart sensitivity across the pair.
Required inputs
- Local civil timestamp
- IANA timezone and tzdb version
- Earlier/later offset evidence or an uncertainty policy
Maha convention
The fact bundle labels the choice as earlier-offset or later-offset. Unresolved folds remain two candidate instants rather than silently selecting the runtime default.
Uncertainty and edge cases
A one-hour fold can materially change the ascendant and houses while leaving slower planetary longitude nearly unchanged.
What this does not establish
Choosing the chart that appears more favorable is not evidence about which occurrence the source meant.
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.