я попробовал вот так
IF OBJECT_ID('TEMPDB..#CommaDate') IS NOT NULL
DROP TABLE #CommaDate
CREATE TABLE #CommaDate
(
DateFormate DATE
)
INSERT INTO #CommaDate VALUES('2018-02-24'),('2018-01-10'),('2017-05-23'),('2017-04-06')
SELECT DISTINCT STUFF((SELECT ',' + CONVERT(VARCHAR(20),DateFormate,101)
FROM #CommaDate
ORDER BY concat(',' , year(CONVERT(VARCHAR(20),DateFormate,101))) desc
FOR XML PATH('')), 1,1, '')
FROM #CommaDate
или
SELECT distinct STUFF((SELECT ',' + CONVERT(VARCHAR(20),DateFormate,101)
FROM #CommaDate
-- ORDER BY concat(',' , year(CONVERT(VARCHAR(20),DateFormate,101))) desc
FOR XML PATH('')), 1,1, '')
FROM #CommaDate
выход
02/24/2018,01/10/2018,05/23/2017,04/06/2017