Date/time/currency formatting localized

Severity: Recommended

Dates, numbers, and currencies format differently across locales:

• Dates: US (MM/DD/YYYY), Europe (DD/MM/YYYY), Japan (YYYY/MM/DD)
• Numbers: US (1,000.00), Germany (1.000,00)
• Currency: Position and symbol vary ($100 vs 100€ vs ¥100)

Check automatically:

# Check for Intl API usage (good sign)
grep -riE "Intl\.(DateTimeFormat|NumberFormat|RelativeTimeFormat)" src/ --include="*.ts" --include="*.tsx" --include="*.js" --include="*.jsx" 2>/dev/null | head -10

# Check for date libraries with locale support
grep -E "date-fns|dayjs|moment|luxon" package.json 2>/dev/null

# Look for locale-aware formatting in date libs
grep -riE "formatDistanceToNow|formatRelative|\.locale\(|\.tz\(" src/ --include="*.ts" --include="*.tsx" --include="*.js" 2>/dev/null | head -10

# Check for i18n library formatting (react-intl, etc.)
grep -riE "FormattedDate|FormattedNumber|FormattedTime|formatDate|formatNumber|formatCurrency" src/ --include="*.ts" --include="*.tsx" 2>/dev/null | head -10

# RED FLAG: Manual date formatting (likely not localized)
grep -riE "toLocaleDateString\(\)|\.toISOString\(\)|MM/DD/YYYY|DD/MM/YYYY" src/ --include="*.ts" --include="*.tsx" 2>/dev/null | head -5

Pass criteria:

• Date/time formatting uses Intl API or locale-aware library
• Currency displays use locale-appropriate formatting
• Timezone handling is explicit (not assumed)

Fail criteria:

• Hardcoded date formats ("MM/DD/YYYY")
• Manual currency symbol placement
• toLocaleDateString() without locale argument (uses system default, inconsistent)

Evidence to capture:

• Date formatting approach
• Number/currency formatting approach
• Libraries in use

---