#standardSQL
WITH `project.dataset.table` AS (
SELECT CURRENT_DATE() AS dt
)
SELECT dt, CAST(dt AS TIMESTAMP) AS ts,
TIMESTAMP(dt) AS ts2
FROM `project.dataset.table`
с результатом как
Row dt ts ts2
1 2018-06-13 2018-06-13 00:00:00.000 UTC 2018-06-13 00:00:00.000 UTC