How To Understand Before Next Day is in Table

Question

 HolidayDate is date which is in Table

 newholiday is Table Name

 Actual_Leave_To is Column Name

 

I Have a Code Given Below-

 

 

 

declare @Actual_Leave_To date= '2016-08-13'

--set @Actual_Leave_To='2016-08-13'

while (select count(1) from newholiday where Holidaydate = @Actual_Leave_To)>0

begin

set @Actual_Leave_To = DATEADD(d,1,@Actual_Leave_To)

end

select @Actual_Leave_To

    

My Question is all  Public holiday date  in my table   newholiday so when is query running then increase 1 day in Actual_Leave_To and this cod is 

working my problem is  i declare 2016-08-13' this day and it add 1 day after running query but i want to know how it will understand when i declare

2016-08-12' next day is  2016-08-13 table and date add 2016-08-14