[kvlonge]

Why

Snowflake types a DATE plus an interval differently depending on where the unit is written. d - INTERVAL '7 days', with the unit inside the quotes, stays a DATE (recorded in temporal/interval_arithmetic.toml). d + INTERVAL '3' DAY and INTERVAL '3' DAYS, with the unit after the quotes, give a TIMESTAMP_NTZ(9) at midnight (recorded in translation data-types-datetime.interval t003_plural). The second spelling converted as a DATE, which changes the column's type and how it compares downstream.

Changes

• A DATE plus or minus INTERVAL 'n' DAY(S) with the unit after the quotes now gives TIMESTAMP_NTZ(9) at midnight plus the days, relying on timestamp_range, as for a timestamp operand. The quoted-unit spelling keeps a DATE.
• The interval rule's conditions say so.

Verification

• Tests that run the converted SQL on DuckDB: '2026-04-01'::DATE + INTERVAL '3' DAYS gives 2026-04-04 00:00:00.000 (it gave 2026-04-04 before the fix), and - INTERVAL '1' DAY across a leap day; the existing quoted-unit DATE case is unchanged.
• No case or corpus file uses the unit-after spelling with a DATE, so no recorded result changes. The held-out t003_plural case can return with this.
• make check-ci, make test-rust, make verify-recorded.

[kvlonge]

D94 gate on 893cb9d (based on main 37e3767):

• make check-ci: exit 0
• make test-rust: passed, every suite exit 0
• make verify-recorded: 11,779 cases, 7,761 passed, 1,031 diverged as expected, 2,951 refused, 0 pending, 0 unproven, 0 failed; 220 of 220 equivalences and rules verified. translation-results: 0 regressions, 0 other changes.
• Hygiene scan: clean.

[kvlonge]

Landing gate at 50e3efb (main 4b6278d merged):

• make check-ci: exit 0
• make test-rust: exit 0
• make verify-recorded: 11,793 cases, 0 failed; nothing regressed against the translation baseline
• Hygiene scan: clean

Merging main pushed conversion/constants.rs over the 2,000-line limit (2,005 lines). 50e3efb moves the unquoted-interval refusal reason inline in intervals.rs, where the other interval refusals already are, and reuses INTERVAL_KIND for the keyword check. Behaviour and message are unchanged. The audits (ee35e0a, 6dd5892) covered the behaviour.