Temporal Localization and Calendar Seed

Space ships a deterministic cldr-seed corpus for the first public Temporal.calendar and Temporal.localization facades. This slice supports a small, exact CLDR 46-derived locale/calendar corpus from checked-in JSON under assets/temporal/icu/cldr-seed/; it does not enable the native ICU4C adapter or import full generated CLDR data.

Public APIs

The public Temporal module exposes two seed-backed namespaces:

• Temporal.calendar.supported-calendars() returns the exact supported calendar ids sorted lexically.
• Temporal.calendar.from-iso(plain-date-time, {:calendar "japanese"}) converts an ISO proleptic Gregorian PlainDateTime into a calendar field record.
• Temporal.calendar.to-iso(calendar-fields) converts a validated calendar field record back to a PlainDateTime.
• Temporal.localization.supported-locales() returns the exact supported locale ids sorted lexically.
• Temporal.localization.supported-combinations() returns supported :locale/:calendar/:date-style rows.
• Temporal.localization.format-plain-date-time(plain-date-time, options) formats only an exact supported combination.
• Temporal.localization.parse-plain-date-time(text, options) parses only exact text emitted by the selected seed pattern and returns a midnight PlainDateTime.

Option keys are canonical only. Unknown options, unknown calendar field keys, unsupported locales, unsupported calendars, unsupported combinations, unsupported styles, malformed localized text, invalid month names, invalid eras, and out-of-range Japanese era dates fail loudly.

Supported seed corpus

The initial locale ids are exactly en-US, fr-FR, and ja-JP. The initial calendar ids are exactly gregory, buddhist, and japanese. Supported :date-style values are exactly :short and :long, and locale ids are exact and case-sensitive.

Locale	Calendar	Date style	Pattern	Example for 2026-10-01
en-US	gregory	:short	MM/DD/YYYY	10/01/2026
en-US	gregory	:long	Month D, YYYY	October 1, 2026
fr-FR	gregory	:short	DD/MM/YYYY	01/10/2026
fr-FR	gregory	:long	D month YYYY	1 octobre 2026
ja-JP	gregory	:short	YYYY/MM/DD	2026/10/01
ja-JP	gregory	:long	YYYY年M月D日	2026年10月1日
en-US	buddhist	:short	MM/DD/YYYY BE	10/01/2569 BE
en-US	buddhist	:long	Month D, YYYY BE	October 1, 2569 BE
ja-JP	japanese	:short	era-code year/MM/DD	R8/10/01
ja-JP	japanese	:long	era-name year年M月D日	令和8年10月1日

The built-in seed corpus provider identity is space.temporal.cldr-seed.

Calendar conversion rules

Calendar conversion is presentation-oriented and separate from exact Duration and Temporal.period arithmetic. The ISO PlainDateTime fields remain the source of truth for time-of-day precision.

• gregory uses era ce with the same year, month, and day as ISO.
• buddhist uses era be with calendar year equal to ISO year plus 543.
• japanese supports only the finite seed era corpus: Showa from 1926-12-25 through 1989-01-07, Heisei from 1989-01-08 through 2019-04-30, and Reiwa from 2019-05-01 onward.

Temporal.calendar.to-iso accepts only calendar field records with keys :kind, :calendar, :era, :year, :month, :day, :hour, :minute, :second, and :nanosecond. Japanese reverse conversion validates that era and date fields are consistent with the supported era boundaries.

Localization format and parse rules

Localization delegates calendar conversion to Temporal.calendar and formats or parses only token patterns from locales.json. Parsing is exact: it consumes the entire input, accepts only seed month and era strings, and does not perform locale negotiation, fallback, numbering-system substitution, relative-time formatting, range formatting, localized timezone names, or natural-language date parsing.

Packaged data and no-network behavior

The selected CLDR seed is packaged under assets/temporal/icu/cldr-seed/ with:

• manifest.json for provenance, supported lists, file list, and no-network metadata.
• calendars.json for finite calendar era/conversion data.
• locales.json for exact locale/calendar/style token data.

The seed is a hand-curated selected subset derived from CLDR 46 date patterns, month names, and era identifiers under the Unicode License v3. Runtime localization and calendar conversion do not fetch network data.

Native ICU4C adapter boundary

The full ICU4C/native adapter remains future work. This slice does not vendor ICU4C source, does not import full generated CLDR data, does not add a native temporal_localization adapter or C++ bindings, and does not enable SPACE_TEMPORAL_ENABLE_ICU_ADAPTER. The native temporal core remains independent from ICU/CLDR presentation and provider policy.

Validation commands

Use the focused localization/calendar validation ladder when changing this surface:

make fennel-check
make constraints
SPACE_DISABLE_AUDIO=1 SKIP_KEYRING_TESTS=1 XDG_DATA_HOME=/tmp/space/tests/xdg-data \
SPACE_ASSETS_PATH=$(pwd)/assets \
FENNEL_PATH="$(pwd)/assets/lua/?.fnl;$(pwd)/assets/lua/?/init.fnl" \
FENNEL_MACRO_PATH="$(pwd)/assets/lua/?.fnl;$(pwd)/assets/lua/?/init.fnl" \
./build/space -m tests.test-temporal-calendar:main
SPACE_DISABLE_AUDIO=1 SKIP_KEYRING_TESTS=1 XDG_DATA_HOME=/tmp/space/tests/xdg-data \
SPACE_ASSETS_PATH=$(pwd)/assets \
FENNEL_PATH="$(pwd)/assets/lua/?.fnl;$(pwd)/assets/lua/?/init.fnl" \
FENNEL_MACRO_PATH="$(pwd)/assets/lua/?.fnl;$(pwd)/assets/lua/?/init.fnl" \
./build/space -m tests.test-temporal-localization:main
python3 -m pytest scripts/tests/test_temporal_dependency_manifests.py -q

For docs-only edits, validate references with the focused rg commands from the task brief.