JavaScript · Dates and internationalisation

Date arithmetic

Dates compare and add through millisecond timestamps. Mutating methods such as setDate exist too.

javascriptRunnable example javascript course

Syntax

date.getTime() + ms

Example

Try it

const start = new Date("2026-01-01T00:00:00Z");
const next = new Date(start.getTime() + 7 * 86400000);
console.log(next.toISOString().slice(0, 10));

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