[fivetran-kwoodbeck]

Snowflake's TIME_SLICE anchors slices to the 1970-01-01 epoch, but the DuckDB transpilation emitted TIME_BUCKET with no origin, so DuckDB used its own default origin and returned the wrong slice for any multi-unit length.

Added an explicit origin to TIME_BUCKET as an extra argument for timeslice_sql:

unit	origin	note
all units	1970-01-01	Snowflake epoch alignment
WEEK	1969-12-29	Monday of the epoch week (WEEK_START=0)

-- Snowflake (source)
SELECT TIME_SLICE(CAST('2021-03-18' AS DATE), 8, 'DAY');  -- 2021-03-18

-- DuckDB (previous transpilation) -> 2021-03-17  (wrong)
SELECT TIME_BUCKET(INTERVAL 8 DAY, CAST('2021-03-18' AS DATE));

-- DuckDB (fixed transpilation) -> 2021-03-18  (correct)
SELECT TIME_BUCKET(INTERVAL 8 DAY, CAST('2021-03-18' AS DATE), CAST('1970-01-01' AS DATE));

[github-actions]

SQLGlot Integration Test Results

✅ All tests passed

Comparing:

• this branch (sqlglot:fix/transpile-duckdb-time-slice @ sqlglot 5a952df)
• baseline (main @ sqlglot c177946)

By Dialect

dialect	main	feature branch	transitions	links
snowflake -> duckdb	1138/1857 passed (61.3%)	1140/1857 passed (61.4%)	2 fail -> pass	full result / delta

Overall

main: 182929 total, 166022 passed (pass rate: 90.8%)

sqlglot:fix/transpile-duckdb-time-slice: 182929 total, 166024 passed (pass rate: 90.8%)

Transitions:
2 fail -> pass

✅ All tests passed

[Copilot]

🟡 Changes recommended

The DuckDB TIME_SLICE change incorrectly converts DATE results to TIMESTAMP and misaligns buckets for StarRocks inputs and Snowflake’s lowercase 'w' alias.

3 open issues

• Normalize week aliases before selecting the origin · New
• Preserve StarRocks time-slice origin semantics · New
• Use a DATE origin for unannotated DATE inputs · New

What changed in this PR

This PR updates SQLGlot’s DuckDB generation for TIME_SLICE to match Snowflake’s epoch-based slice boundaries instead of DuckDB’s default origin.

Changes:

• Adds an explicit 1970-01-01 origin, using 1969-12-29 for Monday-aligned weekly slices.
• Preserves existing end-of-slice handling and DATE casts.
• Adds multi-day and multi-week regression cases and updates transpilation expectations.

File	Description
tests/​dialects/​test_starrocks.py	Updates DuckDB expectations to include explicit origins.
tests/​dialects/​test_snowflake.py	Adds epoch-alignment cases and updates existing expectations.
sqlglot/​generators/​duckdb.py	Supplies typed origins when generating TIME_BUCKET.

_{Review effort: Balanced}