deduct 60 minutes/ 1 hour from punch time (Start time) of attendance Suppose there are 300 employees different kinds of shifting duty they are doing but on 15th October Fingertec machine's clock was stop, so now I want to deduct 60 minutes or 1 hour from their in time. How can I update this in SQL query? Please help me.
Something like this? If you share your table structure the answer could be more precise.

-- TEST TABLE
CREATE TABLE dbo.employees(id int identity(1,1), 
                           StartTime datetime2);

-- TEST VALUE
INSERT INTO dbo.employees (StartTime)
VALUES(getdate());

--CHECK
SELECT * FROM dbo.employees;

-- ACTUAL UPDATE
UPDATE dbo.employees
SET StartTime = DATEADD(hour,-1,StartTime);

-- CHECK AFTER UPDATE
SELECT * FROM dbo.employees;