That's another PIVOT query, lots of cut&paste again.
Assuming you want to count the number of rows matching each day range:
SELECT
COUNT(CASE WHEN CAST(EVENT_TIMESTAMP AS DATE) - CONTRACT_EFFECTIVE_DATE = 1 THEN 1 END) AS "1 day",
COUNT(CASE WHEN CAST(EVENT_TIMESTAMP AS DATE) - CONTRACT_EFFECTIVE_DATE = 2 THEN 1 END) AS "2 day",
COUNT(CASE WHEN CAST(EVENT_TIMESTAMP AS DATE) - CONTRACT_EFFECTIVE_DATE = 3 THEN 1 END) AS "3 day",
COUNT(CASE WHEN CAST(EVENT_TIMESTAMP AS DATE) - CONTRACT_EFFECTIVE_DATE = 4 THEN 1 END) AS "4 day",
...
FROM tab
WHERE CAST(EVENT_TIMESTAMP AS DATE) - CONTRACT_EFFECTIVE_DATE <= 30
You could also put the calculation in a Derived Table, but this just looks simpler:
SELECT
COUNT(CASE WHEN diff = 1 THEN 1 END) AS "1 day",
COUNT(CASE WHEN diff = 2 THEN 1 END) AS "2 day",
COUNT(CASE WHEN diff = 3 THEN 1 END) AS "3 day",
COUNT(CASE WHEN diff = 4 THEN 1 END) AS "4 day"
FROM
(
SELECT CAST(EVENT_TIMESTAMP AS DATE) - CONTRACT_EFFECTIVE_DATE AS diff
FROM tab
WHERE diff <= 30
) AS dt