Here are two queries using a UNION or UNION ALL
/* Combine Process */
SELECT Fld1, Fld2, Fld3, Fld4, NULL AS Late
FROM Table01
WHERE xDate = CONVERT(date, '20240101', 112)
UNION ALL
SELECT Fld1, Fld2, Fld3, Fld4, 1 AS Late
FROM Table01
WHERE xDate < CONVERT(date, '20241201', 112);
Output: