rudeshark.net/packages/backend/src/prelude/time.ts

const dateTimeIntervals = {
	day: 86400000,
	hour: 3600000,
	ms: 1,
};

export function dateUTC(time: number[]): Date {
	const d =
		time.length === 2
			? Date.UTC(time[0], time[1])
			: time.length === 3
			? Date.UTC(time[0], time[1], time[2])
			: time.length === 4
			? Date.UTC(time[0], time[1], time[2], time[3])
			: time.length === 5
			? Date.UTC(time[0], time[1], time[2], time[3], time[4])
			: time.length === 6
			? Date.UTC(time[0], time[1], time[2], time[3], time[4], time[5])
			: time.length === 7
			? Date.UTC(time[0], time[1], time[2], time[3], time[4], time[5], time[6])
			: null;

	if (!d) throw new Error("wrong number of arguments");

	return new Date(d);
}

export function isTimeSame(a: Date, b: Date): boolean {
	return a.getTime() === b.getTime();
}

export function isTimeBefore(a: Date, b: Date): boolean {
	return a.getTime() - b.getTime() < 0;
}

export function isTimeAfter(a: Date, b: Date): boolean {
	return a.getTime() - b.getTime() > 0;
}

export function addTime(
	x: Date,
	value: number,
	span: keyof typeof dateTimeIntervals = "ms",
): Date {
	return new Date(x.getTime() + value * dateTimeIntervals[span]);
}

export function subtractTime(
	x: Date,
	value: number,
	span: keyof typeof dateTimeIntervals = "ms",
): Date {
	return new Date(x.getTime() - value * dateTimeIntervals[span]);
}