First using CURRENT_TIMESTAMP and EXTRACT to get today’s date and month. Then use a CASE statement on MONTH to figure out the quarter:

WITH quarters AS (
  SELECT EXTRACT( MONTH FROM CURRENT_TIMESTAMP ) AS MONTH
) SELECT CURRENT_TIMESTAMP as Today,
         CASE
         WHEN 1 <= MONTH AND MONTH <= 3 THEN 'Q1'
         WHEN 4 <= MONTH AND MONTH <= 6 THEN 'Q2'
         WHEN 7 <= MONTH AND MONTH <= 9 THEN 'Q3'
         ELSE 'Q4'
         END AS Quarters
FROM quarters
;