The blank accessor property of Temporal.Duration instances returns a boolean that is true if this duration represents a zero duration, and false otherwise. It is equivalent to duration.sign === 0.
const d1 = Temporal.Duration.from({ hours: 1, minutes: 30 });
const d2 = Temporal.Duration.from({ hours: -1, minutes: -30 });
const d3 = Temporal.Duration.from({ hours: 0 });
console.log(d1.blank); // false
console.log(d2.blank); // false
console.log(d3.blank); // true