Question: I have two variables `@date` of type `datetime` and `@time` of type `time`. I want to add both to get another `datetime` variable. And I want to perform further calculations on it.

Ex: 

```
Declare @date datetime
Declare @time time

```

I want something like this

```
@date = @date + @time (but not concatenation)

SELECT @Startdate = DATEADD(DAY, -1, @date )

```

Is there any way?

Answer: 
You can tranform your time to seconds and add them to your datetime value:

```
DECLARE @datetime DATETIME = GETDATE(),
        @time TIME = '01:16:24',
        @timeinseconds INT

PRINT 'we add ' + CAST(@time AS VARCHAR(8)) + ' to ' + CONVERT(VARCHAR,@datetime,120)+ ':'

SELECT @timeinseconds = DATEPART(SECOND, @time)
                        + DATEPART(MINUTE, @time) * 60
                        + DATEPART(HOUR, @time) * 3600

SET @datetime = DATEADD(SECOND,@timeinseconds,@datetime)

PRINT 'The result is: ' + CONVERT(VARCHAR,@datetime,120)

```

Output:

```
we add 01:16:24 to 2015-07-17 09:58:45:
The result is: 2015-07-17 11:15:09

```
Your code is correct.

```
DECLARE @date DATETIME = '1/1/2020'
DECLARE @time TIME = '1:00 pm'
DECLARE @Startdate DATETIME

SET @date = @date + @time

SELECT @Startdate = DATEADD(DAY, -1, @date)

@date = 2020-01-01 13:00:00.000
@Startdate = 2019-12-31 13:00:00.000

```

It isn't concatenating, it is adding them together. The time on @date is 0:00:00.000, so it might appear to be concatenating them. But change @date to '1/1/2020 1:00 am' and then:

```
@date = 2020-01-01 14:00:00.000
@Startdate = 2019-12-31 14:00:00.000

```