Dates and Intl

Opening your lesson

A Date represents a timestamp, while a calendar date depends on a time zone. A late UTC timestamp can belong to the following day in Tokyo, and an early UTC timestamp can still belong to the prior day in Los Angeles. Specify the zone when formatting a date for a business rule. For date-only arithmetic in these exercises, use UTC midnight and UTC calendar methods so your machine's local zone cannot change the result. Intl.DateTimeFormat and Intl.NumberFormat let you choose the locale and output options explicitly. Leap days, month rollover, and two-digit padding are checked cases. Avoid slicing an arbitrary localized string to perform calendar arithmetic.

function solve(date: string, days: number): string {
const value = new Date(date + "T00:00:00Z"); value.setUTCDate(value.getUTCDate() + days); return value.toISOString().slice(0, 10);
}

2028-01-01T01:00:00Z is December 31 in Los Angeles. Intl formatting with an explicit timeZone returns the calendar date for that zone.

Choose your character

Your Work Gym account