SQL 126 | yyyy-mm-ddThh:mi:ss.mmm | ISO8601 DateTime Format
Declare @ADate Date,
@ATime Time
Select @ADate='2021-07-12', @ATime='9:05 AM'
Select @ADate AS ADate, @ATime AS ATime
SELECT CONVERT(VARCHAR, CAST(CONVERT(Varchar(15), @ADate, 112) + ' ' + CONVERT(Varchar(8), @ATime) AS DATETIME), 126) AS [SQL ISO8601 DateTime Format]