Word origin · etymology
Descriptive computing label.
Ambiguous names a wall-clock reading with more than one possible instant. Time fold is the backward-clock metaphor used in time-zone software.
How we know · epistemology
Time-zone conversion rule
A backward clock change can map one local reading to two instants. The clock record alone cannot choose between them; an offset, occurrence choice or additional historical evidence is needed.
Connected concepts
Sources & provenance
Use the citations beside each section to distinguish a calculation convention, a historical teaching and an editorial example.