localeaware

Localeaware describes software that uses a user's locale settings to tailor its behavior and presentation. A locale combines language, regional conventions, and cultural norms, and locale-aware programs consult locale data to perform tasks in a way that feels natural to users from different places.

Common areas affected include the formatting and parsing of dates, times, numbers, and currency; text direction and typography; collation (sorting); name and address formatting; pluralization rules; and translations. For example, some locales format dates as day-month-year, others as month-day-year; decimal separators may be commas or periods; and the position of a currency symbol can vary by locale.

Implementation varies by platform. POSIX and C libraries use setlocale and locale categories to enable locale-aware behavior for functions such as strftime and strcoll. Java uses Locale objects and resource bundles. Python offers the locale module and locale-aware formatting utilities. JavaScript provides the Intl API (NumberFormat, DateTimeFormat, Collator) for client-side locale awareness. Data for locale rules commonly come from CLDR, and libraries like ICU provide broader internationalization support.

Locale-awareness is a core concept in internationalization (i18n). Distinguishing locale-aware from locale-agnostic behavior helps avoid confusion and ensures software remains usable across languages and regions.

Challenges include data coverage, inconsistencies across platforms, performance considerations, and complex rules for scripts that are right-to-left or have locale-dependent sorting. Careful design and testing across target locales are essential.