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: 
First of all convert `@date` and `@time` variables to `NVARCHAR()`, then concat them and after It convert It to `DATETIME` datatype. After It you can use `DATEADD` function on It. Try in following:

```
DECLARE @date DATETIME 
DECLARE @time TIME

SET @date = GETDATE()
SET @time = '10:12:13'

SELECT DATEADD(DAY, -1, CAST(CONVERT(NVARCHAR(20), @date, 110) + ' ' +
                             CONVERT(NVARCHAR(20), @time, 108) AS DATETIME))

```

**OUTPUT** (*Today day -1 + time '10:12:13'*):

```
2015-07-16 10:12:13.000

```
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

```