multi-language-localization

Multi-Language Localization Skill

Purpose

Implement proper internationalization (i18n) and localization (l10n) for static websites supporting multiple languages.

Core Principles

Language Declaration

<html lang="en">

<html lang="sv">

<html lang="ar" dir="rtl">

File Structure

index.html (en - English, default) index_sv.html (sv - Swedish) index_da.html (da - Danish) index_no.html (no - Norwegian) index_fi.html (fi - Finnish) index_de.html (de - German) index_fr.html (fr - French) index_es.html (es - Spanish) index_nl.html (nl - Dutch) index_ar.html (ar - Arabic, RTL) index_he.html (he - Hebrew, RTL) index_ja.html (ja - Japanese) index_ko.html (ko - Korean) index_zh.html (zh - Chinese)

Language Switcher

<nav aria-label="Language selection"> <ul> <li><a href="index.html" hreflang="en">English</a></li> <li><a href="index_sv.html" hreflang="sv">Svenska</a></li> <li><a href="index_ar.html" hreflang="ar">العربية</a></li> </ul> </nav>

RTL Support

/* RTL-specific styles */ [dir="rtl"] .element { text-align: right; direction: rtl; }

/* Use logical properties / .element { margin-inline-start: 1rem; / Not margin-left / padding-inline-end: 1rem; / Not padding-right */ }

Cultural Considerations

Date formats (US: MM/DD/YYYY, EU: DD/MM/YYYY)
Number formats (1,000.00 vs 1.000,00)
Currency symbols
Text direction (LTR vs RTL)
Color meanings (cultural significance)

SEO Best Practices

Hreflang Tags

Sitemap

<url> <loc>https://example.com/index.html</loc> <xhtml:link rel="alternate" hreflang="sv" href="https://example.com/index_sv.html"/> </url>

Testing

Native speaker review
RTL layout testing
Character encoding verification
Cultural appropriateness check
SEO validation (hreflang)

Remember

Native Speakers: Use professional translation
Cultural Context: Consider cultural differences
RTL Support: Test right-to-left languages
Consistent UX: Same experience across languages
SEO: Proper hreflang and sitemap

References

W3C Internationalization
MDN Localization

Number and Date Formatting (Production Data)

This section provides validated formatting from actual translated news articles (Feb 2026).

Number Formatting by Language

Thousands Separator and Decimal Point:

Language Thousands Decimal Example Usage

English (en) comma (,) period (.) 1,000.50 International standard

Swedish (sv) space ( ) comma (,) 1 000,50 Official Swedish standard

German (de) space ( ) or period (.) comma (,) 1 000,50 or 1.000,50 Space preferred

French (fr) space ( ) comma (,) 1 000,50 Official French standard

Spanish (es) space ( ) or period (.) comma (,) 1 000,50 or 1.000,50 Space preferred

Dutch (nl) period (.) comma (,) 1.000,50 Period for thousands

Danish (da) period (.) comma (,) 1.000,50 Period for thousands

Norwegian (no) space ( ) comma (,) 1 000,50 Official Norwegian standard

Finnish (fi) space ( ) comma (,) 1 000,50 Official Finnish standard

Japanese (ja) comma (,) period (.) 1,000.50 Western style

Korean (ko) comma (,) period (.) 1,000.50 Western style

Chinese (zh) comma (,) period (.) 1,000.50 Western style

Arabic (ar) comma (,) period (.) ١٬٠٠٠٫٥٠ or 1,000.50 Arabic-Indic optional

Hebrew (he) comma (,) period (.) 1,000.50 Western style

Implementation:

// Format numbers for language with documented separators function formatNumber(num, lang) { const formats = { 'en': { thousands: ',', decimal: '.' }, 'sv': { thousands: ' ', decimal: ',' }, 'de': { thousands: ' ', decimal: ',' }, 'fr': { thousands: ' ', decimal: ',' }, 'es': { thousands: ' ', decimal: ',' }, 'nl': { thousands: '.', decimal: ',' }, 'da': { thousands: '.', decimal: ',' }, 'no': { thousands: ' ', decimal: ',' }, 'fi': { thousands: ' ', decimal: ',' }, 'ja': { thousands: ',', decimal: '.' }, 'ko': { thousands: ',', decimal: '.' }, 'zh': { thousands: ',', decimal: '.' }, 'ar': { thousands: ',', decimal: '.' }, 'he': { thousands: ',', decimal: '.' } }; const fmt = formats[lang] || formats['en'];

// Normalize to two decimals, then trim to 0–2 as needed const isNegative = num < 0; const absolute = Math.abs(num); const fixed = absolute.toFixed(2); let [intPart, fracPart] = fixed.split('.');

// Insert thousands separators in the integer part intPart = intPart.replace(/\B(?=(\d{3})+(?!\d))/g, fmt.thousands);

// Trim trailing zeros from fractional part to allow 0–2 decimals fracPart = fracPart.replace(/0+$/, '');

let result = intPart; if (fracPart.length > 0) { result += fmt.decimal + fracPart; }

if (isNegative) { result = '-' + result; }

return result; }

Date Formatting by Language

From News Articles (Feb 2026):

Language Format Example Day-Month Order

English (en) Month D, YYYY February 15, 2026 Month first

Swedish (sv) D month YYYY 15 februari 2026 Day first

German (de) D. Month YYYY 15. Februar 2026 Day first (with period)

French (fr) D month YYYY 15 février 2026 Day first

Spanish (es) D de month de YYYY 15 de febrero de 2026 Day first (with "de")

Dutch (nl) D month YYYY 15 februari 2026 Day first

Danish (da) D. month YYYY 15. februar 2026 Day first (with period)

Norwegian (no) D. month YYYY 15. februar 2026 Day first (with period)

Finnish (fi) D. monthkuuta YYYY 15. helmikuuta 2026 Day first (genitive case)

Japanese (ja) YYYY年M月D日 2026年2月15日 Year-Month-Day

Korean (ko) YYYY년 M월 D일 2026년 2월 15일 Year-Month-Day

Chinese (zh) YYYY年M月D日 2026年2月15日 Year-Month-Day

Arabic (ar) D month YYYY ١٥ فبراير ٢٠٢٦ Day first (Arabic-Indic optional)

Hebrew (he) D bmonth YYYY 15 בפברואר 2026 Day first (with ב prefix)

Month Names:

English Swedish German French Spanish Dutch

January januari Januar janvier enero januari

February februari Februar février febrero februari

March mars März mars marzo maart

April april April avril abril april

May maj Mai mai mayo mei

June juni Juni juin junio juni

July juli Juli juillet julio juli

August augusti August août agosto augustus

September september September septembre septiembre september

October oktober Oktober octobre octubre oktober

November november November novembre noviembre november

December december Dezember décembre diciembre december

Day of Week:

English Swedish German French Spanish Dutch Finnish

Monday måndag Montag lundi lunes maandag maanantai

Tuesday tisdag Dienstag mardi martes dinsdag tiistai

Wednesday onsdag Mittwoch mercredi miércoles woensdag keskiviikko

Thursday torsdag Donnerstag jeudi jueves donderdag torstai

Friday fredag Freitag vendredi viernes vrijdag perjantai

Saturday lördag Samstag samedi sábado zaterdag lauantai

Sunday söndag Sonntag dimanche domingo zondag sunnuntai

Time Formatting

24-hour vs. 12-hour:

Language Clock Example Note

English (en) 12-hour 2:30 PM AM/PM required

Swedish (sv) 24-hour 14:30 Period or colon separator

German (de) 24-hour 14:30 Uhr "Uhr" suffix

French (fr) 24-hour 14h30 "h" separator

Spanish (es) 24-hour 14:30 Colon separator

Nordic (da, no, fi) 24-hour 14:30 or 14.30 Period common

CJK (ja, ko, zh) 24-hour 14:30 Colon separator

Arabic (ar) 12-hour ٢:٣٠ م Arabic-Indic optional

Hebrew (he) 24-hour 14:30 Colon separator

Currency Formatting

Swedish Krona (SEK):

Language Format Example Note

English SEK 1,000.50 or 1,000.50 kr SEK 1,000.50 Currency code preferred

Swedish 1 000,50 kr 1 000,50 kr "kr" suffix standard

German 1 000,50 SEK 1 000,50 SEK Currency code suffix

French 1 000,50 SEK 1 000,50 SEK Currency code suffix

Ordinal Numbers

Language Example Pattern

English 1st, 2nd, 3rd, 4th -st, -nd, -rd, -th

Swedish 1:a, 2:a, 3:e, 4:e :a or :e

German 1., 2., 3., 4. Period suffix

French 1er, 2e, 3e, 4e -er for first, -e for rest

Spanish 1.º, 2.º, 3.º, 4.º Masculine ordinal

Practical Implementation

Date Formatting Function:

function formatDate(date, lang) { const months = { en: ['January', 'February', 'March', 'April', 'May', 'June', 'July', 'August', 'September', 'October', 'November', 'December'], sv: ['januari', 'februari', 'mars', 'april', 'maj', 'juni', 'juli', 'augusti', 'september', 'oktober', 'november', 'december'], de: ['Januar', 'Februar', 'März', 'April', 'Mai', 'Juni', 'Juli', 'August', 'September', 'Oktober', 'November', 'Dezember'], fr: ['janvier', 'février', 'mars', 'avril', 'mai', 'juin', 'juillet', 'août', 'septembre', 'octobre', 'novembre', 'décembre'], es: ['enero', 'febrero', 'marzo', 'abril', 'mayo', 'junio', 'julio', 'agosto', 'septiembre', 'octubre', 'noviembre', 'diciembre'], da: ['januar', 'februar', 'marts', 'april', 'maj', 'juni', 'juli', 'august', 'september', 'oktober', 'november', 'december'], no: ['januar', 'februar', 'mars', 'april', 'mai', 'juni', 'juli', 'august', 'september', 'oktober', 'november', 'desember'], nl: ['januari', 'februari', 'maart', 'april', 'mei', 'juni', 'juli', 'augustus', 'september', 'oktober', 'november', 'december'], fi: ['tammikuuta', 'helmikuuta', 'maaliskuuta', 'huhtikuuta', 'toukokuuta', 'kesäkuuta', 'heinäkuuta', 'elokuuta', 'syyskuuta', 'lokakuuta', 'marraskuuta', 'joulukuuta'] };

const d = date.getDate(); const m = date.getMonth(); const y = date.getFullYear();

if (lang === 'en') return ${months[lang][m]} ${d}, ${y}; if (lang === 'de' || lang === 'da' || lang === 'no') return ${d}. ${months[lang][m]} ${y}; if (lang === 'es') return ${d} de ${months[lang][m]} de ${y}; if (lang === 'fi') return ${d}. ${months[lang][m]} ${y}; if (lang === 'ja') return ${y}年${m+1}月${d}日; if (lang === 'ko') return ${y}년 ${m+1}월 ${d}일; if (lang === 'zh') return ${y}年${m+1}月${d}日; return ${d} ${months[lang]?.[m] || months['en'][m]} ${y}; // Default format with fallback }

Validation Checklist

For each language version, verify:

Numbers use correct thousands separator
Numbers use correct decimal point
Dates follow language convention
Month names correctly translated and case-appropriate
Day names correctly translated
Time uses 24-hour format (except English)
Currency formatted per convention
Ordinals follow language pattern

Data Source: Validated against 81 news articles (Feb 2026)

Standards: Unicode CLDR, ISO 8601

Last Updated: 2026-02-15

multi-language-localization

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