Try this, hope this will be easy and simple way

--Try option 1

declare @days as int

set @days = 4

declare @dts as datetime

set @dts = GETDATE()

select name, birth_date

from <table name>

where (

CASE WHEN MONTH(birth_date) < MONTH(@dts) THEN (YEAR(@dts) + 1 ) * 10000

ELSE (YEAR(@dts) + 0 ) * 10000

END

) + MONTH(birth_date)*100 + DAY(birth_date) between convert(int,CONVERT(varchar(8), @dts, 112)) and

convert(int,CONVERT(varchar(8), dateadd(d,@days,@dts), 112))

--Or Try option 2 by creating Function which returns Birthdate as per current running year

-- =============================================

-- Author:VINAY M JADIA

-- Create date: 2012-12-31

-- Description:Function will change the year of given month with replacing date

-- =============================================

ALTER FUNCTION [dbo].[ufnChangeYear]

(

-- Add the parameters for the function here

@changingDate datetime,

@withDate datetime

)

RETURNS datetime

AS

BEGIN

-- Declare the return variable here

DECLARE @newDate datetime

SELECT @newDate = CONVERT(varchar(4),(

CASE WHEN MONTH(@changingDate) < MONTH(@withDate) THEN

YEAR(@withDate) + 1

ELSE YEAR(@withDate)

END

)

)+ '/' + RIGHT(CONVERT(VARCHAR(8), @changingDate, 11),5)

RETURN @newDate

END

----Query to fetch result using the newly created function

declare @days int

set @days = 365

declare @dtf datetime, @dtt datetime

set @dtf = CONVERT(datetime, CONVERT(varchar(10), GETDATE(), 111))

set @dtt = DATEADD(D, @days, @dtf)

select name, birth_date

from <tablename>

where dbo.ufnChangeYear(birth_date,getdate()) between @dtf and @dtt

--Hope this will work for n no of days even year, month changing