SQL Server 2019

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CREATE TABLE dbo.YourTable 
(
    mycolumn VARCHAR(10), 
    DateAsDate AS CONVERT(DATE,mycolumn, 102),
    CONSTRAINT CHK_YourTable__ValidDate CHECK (TRY_CONVERT(DATE,mycolumn, 102) IS NOT NULL)
 );
INSERT dbo.YourTable (mycolumn) VALUES('2021.08.10');
1 rows affected

-- INSERTING INVALID DATE WILL NOT WORK
INSERT dbo.YourTable (mycolumn) VALUES('2021.13.10');
Msg 547 Level 16 State 0 Line 2
The INSERT statement conflicted with the CHECK constraint "CHK_YourTable__ValidDate". The conflict occurred in database "fiddle_5d0797f6e088485e8614d605eb406cec", table "dbo.YourTable", column 'mycolumn'.
Msg 3621 Level 0 State 0 Line 2
The statement has been terminated.

-- INSERTING DATE IN WRONG FORMAT WILL NOT WORK
INSERT dbo.YourTable (mycolumn) VALUES('10/08/2021');
Msg 547 Level 16 State 0 Line 2
The INSERT statement conflicted with the CHECK constraint "CHK_YourTable__ValidDate". The conflict occurred in database "fiddle_5d0797f6e088485e8614d605eb406cec", table "dbo.YourTable", column 'mycolumn'.
Msg 3621 Level 0 State 0 Line 2
The statement has been terminated.

SELECT *
FROM dbo.YourTable


mycolumn
DateAsDate


2021.08.10
2021-08-10