Localization

Localization Skill

Helps AI agents correctly format, validate, and explain locale-specific conventions for currency, dates, numbers, units of measurement, and addresses — based on Unicode CLDR standards and real postal/regulatory rules.

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Workflow

1. Identify the locale — Use a BCP 47 locale tag when possible (e.g. de-DE, fr-CA, pt-BR). If only a country name is given, infer the primary locale. If ambiguous (e.g. "Canada"), ask: English or French?

2. Identify the domain(s) — What needs formatting/validating?

   • Currency → read references/currency.md
   • Date / Time → read references/datetime.md
   • Numbers → read references/numbers.md
   • Units of measurement → read references/units.md
   • Address / Phone → read references/addresses.md

3. Apply rules — Use the locale data to:

   • Format: produce a correctly formatted string from raw values
   • Validate: check whether an existing formatted value matches the locale's conventions
   • Fix: reformat an incorrectly formatted value
   • Explain: describe the difference between two locales

4. Output — Respond with the formatted result + a brief note on the rule applied (so the human or downstream agent can understand why, not just what).

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Quick-Reference: Most Common Locales

For full data including edge cases, separators, and address templates, always consult the relevant reference file.

Currency (symbol position · decimal · thousands)

Locale	Country	Example	Symbol	Decimal	Thousands
en-US	USA	$1,234.56	before	.	,
en-GB	UK	£1,234.56	before	.	,
de-DE	Germany	1.234,56 €	after	,	.
nl-NL	Netherlands	€ 1.234,56	before	,	.
fr-FR	France	1 234,56 €	after	,	(nb)
fr-CA	Canada (FR)	1 234,56 $	after	,	(nb)
es-ES	Spain	1.234,56 €	after	,	.
pt-BR	Brazil	R$ 1.234,56	before	,	.
ru-RU	Russia	1 234,56 ₽	after	,	(nb)
tr-TR	Turkey	₺1.234,56	before	,	.
ja-JP	Japan	¥1,234	before	—	,
zh-CN	China	¥1,234.56	before	.	,
ko-KR	South Korea	₩1,234	before	—	,
hi-IN	India	₹12,34,567.00	before	.	lakh
ar-SA	Saudi Arabia	1,234.56 ر.س	after	.	,

(nb) = narrow no-break space U+202F

Date format (short numeric)

Locale	Format	Example	Time
en-US	M/D/YYYY	6/5/2026	12 h
en-GB	DD/MM/YYYY	05/06/2026	24 h
de-DE	DD.MM.YYYY	05.06.2026	24 h
nl-NL	DD-MM-YYYY	05-06-2026	24 h
fr-FR	DD/MM/YYYY	05/06/2026	24 h
es-ES	DD/MM/YYYY	05/06/2026	24 h
pt-BR	DD/MM/YYYY	05/06/2026	24 h
ru-RU	DD.MM.YYYY	05.06.2026	24 h
ja-JP	YYYY/MM/DD	2026/06/05	24 h
zh-CN	YYYY/M/D	2026/6/5	24 h
ko-KR	YYYY.MM.DD	2026.06.05	24 h
ar-SA	DD/MM/YYYY	05/06/2026	12 h

Measurement system

Region	Distance	Temperature	Weight	Volume
USA	miles	°F	lb/oz	fl oz / gal
UK	miles*	°C	kg / st	pints (beer), liters (fuel)
Canada	km	°C	kg	liters
Most of world	km	°C	kg	liters
Myanmar / Liberia	mixed	°C	mixed	mixed

*UK uses miles for road signs but km in most other contexts

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Common Pitfalls to Catch

• Germany vs Netherlands: both use EUR but symbol position is opposite
• France/Russia: thousands separator is narrow no-break space (U+202F), not a regular space
• India: uses lakh/crore grouping — 12,34,567 not 1,234,567
• Japan/Korea: no decimal places for native currencies (¥, ₩)
• US date 06/05: means June 5th — in Europe it means May 6th
• UK mixed units: road distances in miles, most other distances in km; both °C and stones/pounds coexist
• Brazil currency: R$ with a space before the number — not R$1.234, it's R$ 1.234
• Japanese address order: reversed from Western — starts with postal code → prefecture → city → ward → block → building → recipient name

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Reference Files

Load these on-demand based on which domain(s) apply:

Domain	File	When to read
Currency	references/currency.md	Formatting prices, invoice amounts, currency input fields
Date & Time	references/datetime.md	Displaying or parsing dates, timestamps, durations
Numbers	references/numbers.md	Non-currency numbers, percentages, large numbers
Units	references/units.md	Distances, temperatures, weights, volumes
Addresses	references/addresses.md	Address forms, mailing labels, postal validation

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Output Format Guidelines

When formatting for agents / downstream use:

Locale:  de-DE
Domain:  currency
Input:   1234.56 EUR
Output:  1.234,56 €
Rule:    Symbol after amount with space; comma decimal separator; dot thousands separator

When explaining differences for humans:

In Germany (de-DE), the euro sign comes after the number with a space: 1.234,56 €. In the Netherlands (nl-NL), the same amount is written with the euro sign before: € 1.234,56. Both use a comma as the decimal separator and a dot for thousands.

When generating code, prefer using the platform's built-in i18n APIs:

• JS/TS: Intl.NumberFormat, Intl.DateTimeFormat
• Python: babel library or locale module
• Java/Kotlin: java.text.NumberFormat, java.time.format.DateTimeFormatter
• Swift: NumberFormatter, DateFormatter with .locale

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Attribution

Inspired by @MostafaNageeb, who pointed out that trivial-looking formatting differences — like the € sign coming after the number in Germany (14 €) but before in the Netherlands (€ 14) — have a real impact on user trust. These details feel minor until a user notices them.