When you work with international users, displaying dates in their preferred language and regional format is essential. Day.js offers robust locale support, allowing you to easily switch between languages and customize how dates are presented. By default, Day.js uses English, but you can load additional locales and switch between them using the dayjs.locale() function. This affects how months, weekdays, and other date components appear in formatted output. For example, after loading the French locale and setting it as active, formatting a date will use French names for months and days. You can also customize specific locale settings or add your own, making Day.js flexible for a wide range of internationalization needs. This approach ensures that your application is user-friendly for audiences around the world, adapting date displays to their local conventions and expectations.