ReadonlydeltaReadonlyjdReadonlyjdReadonlytimeThe scale the instant was given on and the basis that gave UT1 and TT, as a chart records it.
ReadonlyutcUTC, ISO 8601, to the millisecond; before 1972 and after the IERS table, the civil time read as UT1.
An instant as the engine used it: its UTC, UT1 and TT, and how the time basis gave them.