vremel/src/datetime/startOfSecond.ts

JavaScript date utility library for Temporal API

import type { Temporal } from "../types.js";

/**
 * Returns the start of a second for the given datetime
 * @param dt datetime object which includes time info
 * @returns Temporal object which represents the start of a second
 */
export function startOfSecond<
	DateTime extends
		| Temporal.PlainTime
		| Temporal.PlainDateTime
		| Temporal.ZonedDateTime,
>(dt: DateTime): DateTime {
	// assumption: no sub-second offset transition in timezone database
	return dt.with({ millisecond: 0, microsecond: 0, nanosecond: 0 }) as DateTime;
}