How to calculate Age/Number of Years between two dates [duplicate] - sql

This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
How to calculate age in T-SQL with years, months, and days
On a project I was working on, I was required to calculate a persons age when they join the system; after looking on the internet I found various ways this could be done, but most of them had slight issues when it involved a Leap-Year.
The solution below is how I calculate number of years past / age. Hope this helps others


You need to add the following method to your database:
CREATE FUNCTION [dbo].[fnCalAge] (#DiffFrom DATE, #DiffTo DATE) RETURNS INT
AS
BEGIN
DECLARE #NumOfYears INT
SET #NumOfYears = (SELECT
DATEDIFF(YEAR, #DiffFrom, #DiffTo) +
CASE
WHEN MONTH(#DiffTo) < MONTH(#DiffFrom) THEN -1
WHEN MONTH(#DiffTo) > MONTH(#DiffFrom) THEN 0
ELSE
CASE WHEN DAY(#DiffTo) < DAY(#DiffFrom) THEN -1 ELSE 0 END
END)
IF #NumOfYears < 0
BEGIN
SET #NumOfYears = 0;
END
RETURN #NumOfYears;
END
You then call it in your SQL Query, similar to the following:
SET DATEFORMAT dmy
SELECT dbo.fnCalAge(CAST('20/06/1987' AS DATE), CAST('20/06/2013' AS DATE))


assuming #bDate is datetime of birthdate and #today is todays date, then...
Declare #bDay Date = '31 dec 2000'
Declare #today Date = cast(getdate() as date)
Select datediff(Year, #bDay, #today) -
case When datepart(dayofYear, #today) <
datepart(dayofYear, #bDay) Then 1 Else 0 End


Replace hiredate with DOB for age. Replace sysdate with your date such as to_date('28-DEC-2012') :
SELECT empno, ename, hiredate, TRUNC(MONTHS_BETWEEN(sysdate, hiredate)/12) years_of_service
FROM scott.emp
/

Related

Datetime2 Overflow Issue [duplicate]

I have a table listing people along with their date of birth (currently a nvarchar(25))
How can I convert that to a date, and then calculate their age in years?
My data looks as follows
ID Name DOB
1 John 1992-01-09 00:00:00
2 Sally 1959-05-20 00:00:00
I would like to see:
ID Name AGE DOB
1 John 17 1992-01-09 00:00:00
2 Sally 50 1959-05-20 00:00:00

There are issues with leap year/days and the following method, see the update below:
try this:
DECLARE #dob datetime
SET #dob='1992-01-09 00:00:00'
SELECT DATEDIFF(hour,#dob,GETDATE())/8766.0 AS AgeYearsDecimal
,CONVERT(int,ROUND(DATEDIFF(hour,#dob,GETDATE())/8766.0,0)) AS AgeYearsIntRound
,DATEDIFF(hour,#dob,GETDATE())/8766 AS AgeYearsIntTrunc
OUTPUT:
AgeYearsDecimal AgeYearsIntRound AgeYearsIntTrunc
--------------------------------------- ---------------- ----------------
17.767054 18 17
(1 row(s) affected)
UPDATE here are some more accurate methods:
BEST METHOD FOR YEARS IN INT
DECLARE #Now datetime, #Dob datetime
SELECT #Now='1990-05-05', #Dob='1980-05-05' --results in 10
--SELECT #Now='1990-05-04', #Dob='1980-05-05' --results in 9
--SELECT #Now='1989-05-06', #Dob='1980-05-05' --results in 9
--SELECT #Now='1990-05-06', #Dob='1980-05-05' --results in 10
--SELECT #Now='1990-12-06', #Dob='1980-05-05' --results in 10
--SELECT #Now='1991-05-04', #Dob='1980-05-05' --results in 10
SELECT
(CONVERT(int,CONVERT(char(8),#Now,112))-CONVERT(char(8),#Dob,112))/10000 AS AgeIntYears
you can change the above 10000 to 10000.0 and get decimals, but it will not be as accurate as the method below.
BEST METHOD FOR YEARS IN DECIMAL
DECLARE #Now datetime, #Dob datetime
SELECT #Now='1990-05-05', #Dob='1980-05-05' --results in 10.000000000000
--SELECT #Now='1990-05-04', #Dob='1980-05-05' --results in 9.997260273973
--SELECT #Now='1989-05-06', #Dob='1980-05-05' --results in 9.002739726027
--SELECT #Now='1990-05-06', #Dob='1980-05-05' --results in 10.002739726027
--SELECT #Now='1990-12-06', #Dob='1980-05-05' --results in 10.589041095890
--SELECT #Now='1991-05-04', #Dob='1980-05-05' --results in 10.997260273973
SELECT 1.0* DateDiff(yy,#Dob,#Now)
+CASE
WHEN #Now >= DATEFROMPARTS(DATEPART(yyyy,#Now),DATEPART(m,#Dob),DATEPART(d,#Dob)) THEN --birthday has happened for the #now year, so add some portion onto the year difference
( 1.0 --force automatic conversions from int to decimal
* DATEDIFF(day,DATEFROMPARTS(DATEPART(yyyy,#Now),DATEPART(m,#Dob),DATEPART(d,#Dob)),#Now) --number of days difference between the #Now year birthday and the #Now day
/ DATEDIFF(day,DATEFROMPARTS(DATEPART(yyyy,#Now),1,1),DATEFROMPARTS(DATEPART(yyyy,#Now)+1,1,1)) --number of days in the #Now year
)
ELSE --birthday has not been reached for the last year, so remove some portion of the year difference
-1 --remove this fractional difference onto the age
* ( -1.0 --force automatic conversions from int to decimal
* DATEDIFF(day,DATEFROMPARTS(DATEPART(yyyy,#Now),DATEPART(m,#Dob),DATEPART(d,#Dob)),#Now) --number of days difference between the #Now year birthday and the #Now day
/ DATEDIFF(day,DATEFROMPARTS(DATEPART(yyyy,#Now),1,1),DATEFROMPARTS(DATEPART(yyyy,#Now)+1,1,1)) --number of days in the #Now year
)
END AS AgeYearsDecimal

Gotta throw this one out there. If you convert the date using the 112 style (yyyymmdd) to a number you can use a calculation like this...
(yyyyMMdd - yyyyMMdd) / 10000 = difference in full years
declare #as_of datetime, #bday datetime;
select #as_of = '2009/10/15', #bday = '1980/4/20'
select
Convert(Char(8),#as_of,112),
Convert(Char(8),#bday,112),
0 + Convert(Char(8),#as_of,112) - Convert(Char(8),#bday,112),
(0 + Convert(Char(8),#as_of,112) - Convert(Char(8),#bday,112)) / 10000
output
20091015 19800420 290595 29

I have used this query in our production code for nearly 10 years:
SELECT FLOOR((CAST (GetDate() AS INTEGER) - CAST(Date_of_birth AS INTEGER)) / 365.25) AS Age

You need to consider the way the datediff command rounds.
SELECT CASE WHEN dateadd(year, datediff (year, DOB, getdate()), DOB) > getdate()
THEN datediff(year, DOB, getdate()) - 1
ELSE datediff(year, DOB, getdate())
END as Age
FROM <table>
Which I adapted from here.
Note that it will consider 28th February as the birthday of a leapling for non-leap years e.g. a person born on 29 Feb 2020 will be considered 1 year old on 28 Feb 2021 instead of 01 Mar 2021.

So many of the above solutions are wrong DateDiff(yy,#Dob, #PassedDate) will not consider the month and day of both dates. Also taking the dart parts and comparing only works if they're properly ordered.
THE FOLLOWING CODE WORKS AND IS VERY SIMPLE:
create function [dbo].[AgeAtDate](
#DOB datetime,
#PassedDate datetime
)
returns int
with SCHEMABINDING
as
begin
declare #iMonthDayDob int
declare #iMonthDayPassedDate int
select #iMonthDayDob = CAST(datepart (mm,#DOB) * 100 + datepart (dd,#DOB) AS int)
select #iMonthDayPassedDate = CAST(datepart (mm,#PassedDate) * 100 + datepart (dd,#PassedDate) AS int)
return DateDiff(yy,#DOB, #PassedDate)
- CASE WHEN #iMonthDayDob <= #iMonthDayPassedDate
THEN 0
ELSE 1
END
End

EDIT: THIS ANSWER IS INCORRECT. I leave it in here as a warning to anyone tempted to use dayofyear, with a further edit at the end.
If, like me, you do not want to divide by fractional days or risk rounding/leap year errors, I applaud #Bacon Bits comment in a post above https://stackoverflow.com/a/1572257/489865 where he says:
If we're talking about human ages, you should calculate it the way
humans calculate age. It has nothing to do with how fast the earth
moves and everything to do with the calendar. Every time the same
month and day elapses as the date of birth, you increment age by 1.
This means the following is the most accurate because it mirrors what
humans mean when they say "age".
He then offers:
DATEDIFF(yy, #date, GETDATE()) -
CASE WHEN (MONTH(#date) > MONTH(GETDATE())) OR (MONTH(#date) = MONTH(GETDATE()) AND DAY(#date) > DAY(GETDATE()))
THEN 1 ELSE 0 END
There are several suggestions here involving comparing the month & day (and some get it wrong, failing to allow for the OR as correctly here!). But nobody has offered dayofyear, which seems so simple and much shorter. I offer:
DATEDIFF(year, #date, GETDATE()) -
CASE WHEN DATEPART(dayofyear, #date) > DATEPART(dayofyear, GETDATE()) THEN 1 ELSE 0 END
[Note: Nowhere in SQL BOL/MSDN is what DATEPART(dayofyear, ...) returns actually documented! I understand it to be a number in the range 1--366; most importantly, it does not change by locale as per DATEPART(weekday, ...) & SET DATEFIRST.]
EDIT: Why dayofyear goes wrong: As user #AeroX has commented, if the birth/start date is after February in a non leap year, the age is incremented one day early when the current/end date is a leap year, e.g. '2015-05-26', '2016-05-25' gives an age of 1 when it should still be 0. Comparing the dayofyear in different years is clearly dangerous. So using MONTH() and DAY() is necessary after all.

I believe this is similar to other ones posted here.... but this solution worked for the leap year examples 02/29/1976 to 03/01/2011 and also worked for the case for the first year.. like 07/04/2011 to 07/03/2012 which the last one posted about leap year solution did not work for that first year use case.
SELECT FLOOR(DATEDIFF(DAY, #date1 , #date2) / 365.25)
Found here.

Since there isn't one simple answer that always gives the correct age, here's what I came up with.
SELECT DATEDIFF(YY, DateOfBirth, GETDATE()) -
CASE WHEN RIGHT(CONVERT(VARCHAR(6), GETDATE(), 12), 4) >=
RIGHT(CONVERT(VARCHAR(6), DateOfBirth, 12), 4)
THEN 0 ELSE 1 END AS AGE
This gets the year difference between the birth date and the current date. Then it subtracts a year if the birthdate hasn't passed yet.
Accurate all the time - regardless of leap years or how close to the birthdate.
Best of all - no function.

I've done a lot of thinking and searching about this and I have 3 solutions that
calculate age correctly
are short (mostly)
are (mostly) very understandable.
Here are testing values:
DECLARE #NOW DATETIME = '2013-07-04 23:59:59'
DECLARE #DOB DATETIME = '1986-07-05'
Solution 1: I found this approach in one js library. It's my favourite.
DATEDIFF(YY, #DOB, #NOW) -
CASE WHEN DATEADD(YY, DATEDIFF(YY, #DOB, #NOW), #DOB) > #NOW THEN 1 ELSE 0 END
It's actually adding difference in years to DOB and if it is bigger than current date then subtracts one year. Simple right? The only thing is that difference in years is duplicated here.
But if you don't need to use it inline you can write it like this:
DECLARE #AGE INT = DATEDIFF(YY, #DOB, #NOW)
IF DATEADD(YY, #AGE, #DOB) > #NOW
SET #AGE = #AGE - 1
Solution 2: This one I originally copied from #bacon-bits. It's the easiest to understand but a bit long.
DATEDIFF(YY, #DOB, #NOW) -
CASE WHEN MONTH(#DOB) > MONTH(#NOW)
OR MONTH(#DOB) = MONTH(#NOW) AND DAY(#DOB) > DAY(#NOW)
THEN 1 ELSE 0 END
It's basically calculating age as we humans do.
Solution 3: My friend refactored it into this:
DATEDIFF(YY, #DOB, #NOW) -
CEILING(0.5 * SIGN((MONTH(#DOB) - MONTH(#NOW)) * 50 + DAY(#DOB) - DAY(#NOW)))
This one is the shortest but it's most difficult to understand. 50 is just a weight so the day difference is only important when months are the same. SIGN function is for transforming whatever value it gets to -1, 0 or 1. CEILING(0.5 * is the same as Math.max(0, value) but there is no such thing in SQL.

What about:
DECLARE #DOB datetime
SET #DOB='19851125'
SELECT Datepart(yy,convert(date,GETDATE())-#DOB)-1900
Wouldn't that avoid all those rounding, truncating and ofsetting issues?

Just check whether the below answer is feasible.
DECLARE #BirthDate DATE = '09/06/1979'
SELECT
(
YEAR(GETDATE()) - YEAR(#BirthDate) -
CASE WHEN (MONTH(GETDATE()) * 100) + DATEPART(dd, GETDATE()) >
(MONTH(#BirthDate) * 100) + DATEPART(dd, #BirthDate)
THEN 1
ELSE 0
END
)

select floor((datediff(day,0,#today) - datediff(day,0,#birthdate)) / 365.2425) as age
There are a lot of 365.25 answers here. Remember how leap years are defined:
Every four years
except every 100 years
except every 400 years

There are many answers to this question, but I think this one is close to the truth.
The datediff(year,…,…) function, as we all know, only counts the boundaries crossed by the date part, in this case the year. As a result it ignores the rest of the year.
This will only give the age in completed years if the year were to start on the birthday. It probably doesn’t, but we can fake it by adjusting the asking date back by the same amount.
In pseudopseudo code, it’s something like this:
adjusted_today = today - month(dob) + 1 - day(dob) + 1
age = year(adjusted_today - dob)
The + 1 is to allow for the fact that the month and day numbers start from 1 and not 0.
The reason we subtract the month and the day separately rather than the day of the year is because February has the annoying tendency to change its length.
The calculation in SQL is:
datediff(year,dob,dateadd(month,-month(dob)+1,dateadd(day,-day(dob)+1,today)))
where dob and today are presumed to be the date of birth and the asking date.
You can test this as follows:
WITH dates AS (
SELECT
cast('2022-03-01' as date) AS today,
cast('1943-02-25' as date) AS dob
)
select
datediff(year,dob,dateadd(month,-month(dob)+1,dateadd(day,-day(dob)+1,today))) AS age
from dates;
which gives you George Harrison’s age in completed years.
This is much cleaner than fiddling about with quarter days which will generally give you misleading values on the edges.
If you have the luxury of creating a scalar function, you can use something like this:
DROP FUNCTION IF EXISTS age;
GO
CREATE FUNCTION age(#dob date, #today date) RETURNS INT AS
BEGIN
SET #today = dateadd(month,-month(#dob)+1,#today);
SET #today = dateadd(day,-day(#dob)+1,#today);
RETURN datediff(year,#dob,#today);
END;
GO
Remember, you need to call dbo.age() because, well, Microsoft.

DECLARE #DOB datetime
set #DOB ='11/25/1985'
select floor(
( cast(convert(varchar(8),getdate(),112) as int)-
cast(convert(varchar(8),#DOB,112) as int) ) / 10000
)
source: http://beginsql.wordpress.com/2012/04/26/how-to-calculate-age-in-sql-server/

Try This
DECLARE #date datetime, #tmpdate datetime, #years int, #months int, #days int
SELECT #date = '08/16/84'
SELECT #tmpdate = #date
SELECT #years = DATEDIFF(yy, #tmpdate, GETDATE()) - CASE WHEN (MONTH(#date) > MONTH(GETDATE())) OR (MONTH(#date) = MONTH(GETDATE()) AND DAY(#date) > DAY(GETDATE())) THEN 1 ELSE 0 END
SELECT #tmpdate = DATEADD(yy, #years, #tmpdate)
SELECT #months = DATEDIFF(m, #tmpdate, GETDATE()) - CASE WHEN DAY(#date) > DAY(GETDATE()) THEN 1 ELSE 0 END
SELECT #tmpdate = DATEADD(m, #months, #tmpdate)
SELECT #days = DATEDIFF(d, #tmpdate, GETDATE())
SELECT Convert(Varchar(Max),#years)+' Years '+ Convert(Varchar(max),#months) + ' Months '+Convert(Varchar(Max), #days)+'days'

After trying MANY methods, this works 100% of the time using the modern MS SQL FORMAT function instead of convert to style 112. Either would work but this is the least code.
Can anyone find a date combination which does not work? I don't think there is one :)
--Set parameters, or choose from table.column instead:
DECLARE #DOB DATE = '2000/02/29' -- If #DOB is a leap day...
,#ToDate DATE = '2018/03/01' --...there birthday in this calculation will be
--0+ part tells SQL to calc the char(8) as numbers:
SELECT [Age] = (0+ FORMAT(#ToDate,'yyyyMMdd') - FORMAT(#DOB,'yyyyMMdd') ) /10000

CASE WHEN datepart(MM, getdate()) < datepart(MM, BIRTHDATE) THEN ((datepart(YYYY, getdate()) - datepart(YYYY, BIRTH_DATE)) -1 )
ELSE
CASE WHEN datepart(MM, getdate()) = datepart(MM, BIRTHDATE)
THEN
CASE WHEN datepart(DD, getdate()) < datepart(DD, BIRTHDATE) THEN ((datepart(YYYY, getdate()) - datepart(YYYY, BIRTHDATE)) -1 )
ELSE (datepart(YYYY, getdate()) - datepart(YYYY, BIRTHDATE))
END
ELSE (datepart(YYYY, getdate()) - datepart(YYYY, BIRTHDATE)) END
END

SELECT ID,
Name,
DATEDIFF(yy,CONVERT(DATETIME, DOB),GETDATE()) AS AGE,
DOB
FROM MyTable

How about this:
SET #Age = CAST(DATEDIFF(Year, #DOB, #Stamp) as int)
IF (CAST(DATEDIFF(DAY, DATEADD(Year, #Age, #DOB), #Stamp) as int) < 0)
SET #Age = #Age - 1

Try this solution:
declare #BirthDate datetime
declare #ToDate datetime
set #BirthDate = '1/3/1990'
set #ToDate = '1/2/2008'
select #BirthDate [Date of Birth], #ToDate [ToDate],(case when (DatePart(mm,#ToDate) < Datepart(mm,#BirthDate))
OR (DatePart(m,#ToDate) = Datepart(m,#BirthDate) AND DatePart(dd,#ToDate) < Datepart(dd,#BirthDate))
then (Datepart(yy, #ToDate) - Datepart(yy, #BirthDate) - 1)
else (Datepart(yy, #ToDate) - Datepart(yy, #BirthDate))end) Age

This will correctly handle the issues with the birthday and rounding:
DECLARE #dob datetime
SET #dob='1992-01-09 00:00:00'
SELECT DATEDIFF(YEAR, '0:0', getdate()-#dob)

Ed Harper's solution is the simplest I have found which never returns the wrong answer when the month and day of the two dates are 1 or less days apart. I made a slight modification to handle negative ages.
DECLARE #D1 AS DATETIME, #D2 AS DATETIME
SET #D2 = '2012-03-01 10:00:02'
SET #D1 = '2013-03-01 10:00:01'
SELECT
DATEDIFF(YEAR, #D1,#D2)
+
CASE
WHEN #D1<#D2 AND DATEADD(YEAR, DATEDIFF(YEAR,#D1, #D2), #D1) > #D2
THEN - 1
WHEN #D1>#D2 AND DATEADD(YEAR, DATEDIFF(YEAR,#D1, #D2), #D1) < #D2
THEN 1
ELSE 0
END AS AGE

The answer marked as correct is nearer to accuracy but, it fails in following scenario - where Year of birth is Leap year and day are after February month
declare #ReportStartDate datetime = CONVERT(datetime, '1/1/2014'),
#DateofBirth datetime = CONVERT(datetime, '2/29/1948')
FLOOR(DATEDIFF(HOUR,#DateofBirth,#ReportStartDate )/8766)
OR
FLOOR(DATEDIFF(HOUR,#DateofBirth,#ReportStartDate )/8765.82) -- Divisor is more accurate than 8766
-- Following solution is giving me more accurate results.
FLOOR(DATEDIFF(YEAR,#DateofBirth,#ReportStartDate) - (CASE WHEN DATEADD(YY,DATEDIFF(YEAR,#DateofBirth,#ReportStartDate),#DateofBirth) > #ReportStartDate THEN 1 ELSE 0 END ))
It worked in almost all scenarios, considering leap year, date as 29 feb, etc.
Please correct me if this formula have any loophole.

Declare #dob datetime
Declare #today datetime
Set #dob = '05/20/2000'
set #today = getdate()
select CASE
WHEN dateadd(year, datediff (year, #dob, #today), #dob) > #today
THEN datediff (year, #dob, #today) - 1
ELSE datediff (year, #dob, #today)
END as Age

Here is how i calculate age given a birth date and current date.
select case
when cast(getdate() as date) = cast(dateadd(year, (datediff(year, '1996-09-09', getdate())), '1996-09-09') as date)
then dateDiff(yyyy,'1996-09-09',dateadd(year, 0, getdate()))
else dateDiff(yyyy,'1996-09-09',dateadd(year, -1, getdate()))
end as MemberAge
go

CREATE function dbo.AgeAtDate(
#DOB datetime,
#CompareDate datetime
)
returns INT
as
begin
return CASE WHEN #DOB is null
THEN
null
ELSE
DateDiff(yy,#DOB, #CompareDate)
- CASE WHEN datepart(mm,#CompareDate) > datepart(mm,#DOB) OR (datepart(mm,#CompareDate) = datepart(mm,#DOB) AND datepart(dd,#CompareDate) >= datepart(dd,#DOB))
THEN 0
ELSE 1
END
END
End
GO

DECLARE #FromDate DATETIME = '1992-01-2623:59:59.000',
#ToDate DATETIME = '2016-08-10 00:00:00.000',
#Years INT, #Months INT, #Days INT, #tmpFromDate DATETIME
SET #Years = DATEDIFF(YEAR, #FromDate, #ToDate)
- (CASE WHEN DATEADD(YEAR, DATEDIFF(YEAR, #FromDate, #ToDate),
#FromDate) > #ToDate THEN 1 ELSE 0 END)
SET #tmpFromDate = DATEADD(YEAR, #Years , #FromDate)
SET #Months = DATEDIFF(MONTH, #tmpFromDate, #ToDate)
- (CASE WHEN DATEADD(MONTH,DATEDIFF(MONTH, #tmpFromDate, #ToDate),
#tmpFromDate) > #ToDate THEN 1 ELSE 0 END)
SET #tmpFromDate = DATEADD(MONTH, #Months , #tmpFromDate)
SET #Days = DATEDIFF(DAY, #tmpFromDate, #ToDate)
- (CASE WHEN DATEADD(DAY, DATEDIFF(DAY, #tmpFromDate, #ToDate),
#tmpFromDate) > #ToDate THEN 1 ELSE 0 END)
SELECT #FromDate FromDate, #ToDate ToDate,
#Years Years, #Months Months, #Days Days

What about a solution with only date functions, not math, not worries about leap year
CREATE FUNCTION dbo.getAge(#dt datetime)
RETURNS int
AS
BEGIN
RETURN
DATEDIFF(yy, #dt, getdate())
- CASE
WHEN
MONTH(#dt) > MONTH(GETDATE()) OR
(MONTH(#dt) = MONTH(GETDATE()) AND DAY(#dt) > DAY(GETDATE()))
THEN 1
ELSE 0
END
END

declare #birthday as datetime
set #birthday = '2000-01-01'
declare #today as datetime
set #today = GetDate()
select
case when ( substring(convert(varchar, #today, 112), 5,4) >= substring(convert(varchar, #birthday, 112), 5,4) ) then
(datepart(year,#today) - datepart(year,#birthday))
else
(datepart(year,#today) - datepart(year,#birthday)) - 1
end

The following script checks the difference in years between now and the given date of birth; the second part checks whether the birthday is already past in the current year; if not, it subtracts it:
SELECT year(NOW()) - year(date_of_birth) - (CONCAT(year(NOW()), '-', month(date_of_birth), '-', day(date_of_birth)) > NOW()) AS Age
FROM tableName;

SQL query to find employee aniversary

I need to find anniversary date and anniversary year of employees and send email in every 14 days.But I have a problem with last week of December when using the following query if start date and end date are in different years.
Select * from Resource
where (DATEPART(dayofyear,JoinDate)
BETWEEN DATEPART(dayofyear,GETDATE())
AND DATEPART(dayofyear,DateAdd(DAY,14,GETDATE())))

Instead of comparing to a dayofyear (which resets to zero at jan 1st and is the reason your query breaks within 14 days of the end of the year) you could update the employee's joindate to be the current year for the purpose of the query and just compare to actual dates
Select * from Resource
-- Add the number of years difference between joinDate and the current year
where DATEADD(year,DATEDIFF(Year,joinDate,GetDate()),JoinDate)
-- compare to range "today"
BETWEEN GetDate()
-- to 14 days from today
AND DATEADD(Day,14,GetDate())
-- duplicate for following year
OR DATEADD(year,DATEDIFF(Year,joinDate,GetDate())+1,JoinDate) -- 2016-1-1
BETWEEN GetDate()
AND DATEADD(Day,14,GetDate())
Test query:
declare #joindate DATETIME='2012-1-1'
declare #today DATETIME = '2015-12-26'
SELECT #joinDate
where DATEADD(year,DATEDIFF(Year,#joinDate,#today),#JoinDate) -- 2015-1-1
BETWEEN #today -- 2015-12-26
AND DATEADD(Day,14,#today) -- 2016-01-09
OR DATEADD(year,DATEDIFF(Year,#joinDate,#today)+1,#JoinDate) -- 2016-1-1
BETWEEN #today -- 2015-12-26
AND DATEADD(Day,14,#today) -- 2016-01-09
(H/T #Damien_The_Unbeliever for a simple fix)
The above correctly selects the joinDate which is in the first week of Jan (note I've had to fudge #today as Ive not managed to invent time travel).
The above solution should also solve the issue with leap years that was hiding in your original solution.
Update
You expressed in comments the requirement to select AnniversaryDate and Years of service, you need to apply some CASE logic to determine whether to add 1 (year or date) to your select
select *,
CASE
WHEN DATEADD(YEAR,DATEDIFF(Year,JoinDate,GETDATE()),JoinDate) < GetDate()
THEN DATEDIFF(Year,JoinDate,GETDATE())+1
ELSE DATEDIFF(Year,JoinDate,GETDATE())
END as [Years],
CASE WHEN DATEADD(YEAR,DATEDIFF(Year,JoinDate,GETDATE()),JoinDate) < GetDate()
THEN DATEADD(YEAR,DATEDIFF(Year,JoinDate,GETDATE())+1,JoinDate)
ELSE DATEADD(YEAR,DATEDIFF(Year,JoinDate,GETDATE()),JoinDate)
end as [AnniversaryDate]
.... // etc

You could do this:
Select * from Resource
where DATEPART(dayofyear,JoinDate)
BETWEEN DATEPART(dayofyear,GETDATE())
AND DATEPART(dayofyear,DateAdd(DAY,14,GETDATE()))
OR
DATEPART(dayofyear,JoinDate)
BETWEEN (DATEPART(dayofyear,GETDATE()) + 365)
AND (DATEPART(dayofyear,DateAdd(DAY,14,GETDATE())) + 365)

Try this:
DECLARE #Today DATE = GETDATE() --'12/25/2013'
DECLARE #Duration INT = 14
;WITH Recur AS
(
SELECT #Today AS RecurDate
UNION ALL
SELECT DATEADD(DAY, 1, RecurDate)
FROM Recur
WHERE DATEDIFF(DAY, #Today, RecurDate)+1 < #Duration
)
SELECT
r.*
FROM
Resource r
JOIN Recur
ON CONVERT(VARCHAR(5), JoinDate, 101) = CONVERT(VARCHAR(5), RecurDate, 101)
WHERE JoinDate < #Today

You can use the SQL DATEADD() function with week number parameter
Here is how you can use it:
DECLARE #date date = getdate()
Select * from Resource
where
JoinDate BETWEEN #date AND DATEADD(ww,2,#date)

Function that calculates age in SQL

I'm looking for a way to calculate the age of a person. I'm making a function for it that I can use later as well as this time.
Function should take a ID-Number which are 11 characters in sweden format which is 560404-1234.
And return the age of the person just the years. So far I've thought of making a subtraction with example: Getdate year 2014 - 19+IDNr datepart yy to get the sum.
Still stuck though.
Cheers

I am guessing that the Swedish id number format is YYMMDD followed by something else.
If so, then the following should work to get the date:
select cast('19'+left(idn, 6) as date)
Then the age would be:
select datediff(year, cast('19'+left(idn, 6) as date), getdate())
What do the Swedes do about people born in the last 14 or so years? What happens to those who are over 100 years old?

If "dean" is correct, then you can try following code,
Create FUNCTION [dbo].[udfn_Get_Age_In_Years]
(
#ID_Number varchar(50)
)
Returns int
--select dbo.[udfn_Get_Age_In_Years]('560404-1234')
as
begin
Declare #retVal int = 0
select #retVal = Datediff(mm,col_dob,GETDATE()) / 12 from myTable
where ID_Number = #ID_Number
Return #retVal
end

This is my answer it's similar to the above ones but this is how I've solved it after a while.
ALTER function [dbo].[Function_AGE]
(
#IdNr varchar(13)
)
returns int
as
begin
Declare #Calc int
Set #IdNr = (Select Case when LEN(#IdNr) > 11
then cast(left(#IdNr, 8) as date)
else cast('19'+left(#IdNr,6) as date) end)
set #Calc = (select datediff(year,#IdNr,getdate()))
Return #Calc
end

Here is how you would calculate age of a person, given their age and current date
select case
when cast(getdate() as date) = cast(dateadd(year, (datediff(year, '1996-09-09', getdate())), '1996-09-09') as date)
then dateDiff(yyyy,'1996-09-09',dateadd(year, 0, getdate()))
else dateDiff(yyyy,'1996-09-09',dateadd(year, -1, getdate()))
end as MemberAge
go

To Compare a birthdate to #Date, the DATEDIFF gets you close. Subtract off of that if the month and day haven't occurred yet in the year.
CASE WHEN DATEPART(mm,birthdate) > DATEPART(mm,#Date)
THEN DATEDIFF(YEAR, birthdate AS DATE), #Date) - 1
WHEN DATEPART(mm,birthdate) = DATEPART(mm,#Date)
AND DATEPART(dd,birthdate) > DATEPART(dd,#Date)
THEN DATEDIFF(YEAR, birthdate AS DATE), #Date) - 1
ELSE DATEDIFF(YEAR, CAST(birthdate AS DATE), #Date)
END AS Age

Age Calculation Query [duplicate]

This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
How to calculate age in T-SQL with years, months, and days
calculating age from sysdate and birthdate using SQL Server
In the process of some age calculations. I'm a bit of a novice when it comes to SQL but I've been tasked with singling out persons who will turn 65yrs old as of 31 March 2013. So far I'm able to calculate age based on given DOB, however I'm having issues singling out these persons. I'm thinking this is a simple issue but I'm stumped, see sql statement. Can someone please point me in the right direction.
SELECT ip_master.ssn, ip_master.firstname, ip_master.surname, ip_master.status,
CASE WHEN DATEADD(YEAR, DATEDIFF (YEAR, dob, '2013/03/31'), dob) > '2013/03/31'
THEN DATEDIFF(YEAR, dob, '2013/03/31') - 1
ELSE DATEDIFF(YEAR, dob, '2013/03/31')
END AS 'Age'
FROM test_db.dbo.ip_master ip_master

Append a WHERE clause to your statement:
...
WHERE dob = '1948-03-31'

Would the following do? I just buried your query inside another query and applied restriction on age.
select * from
(
SELECT ip_master.ssn, ip_master.firstname, ip_master.surname, ip_master.status,
CASE WHEN DATEADD(YEAR, DATEDIFF (YEAR, dob, '2013/03/31'), dob) > '2013/03/31'
THEN DATEDIFF(YEAR, dob, '2013/03/31') - 1
ELSE DATEDIFF(YEAR, dob, '2013/03/31')
END AS 'Age'
FROM test_db.dbo.ip_master ip_master
)
where Age >= 65

Try the Below Query... it will work perfectly...
DECLARE #CalDate datetime;
DECLARE #CurDate datetime;
Declare #count INT
SET #CalDate ='03/31/2013'
SET #count =0
SELECT #CurDate = DateAdd(Month, 1, #CalDate)
SET #count = #count + datepart(dd,dateadd(dd,-1,dateadd(mm,1,cast(cast(year(#CurDate) as varchar)+'-'+cast(month(#CurDate) as varchar)+'-01' as datetime))))
SELECT ip_master.ssn, ip_master.firstname, ip_master.surname, ip_master.status,DATEDIFF (yy, DOB, cast(#CalDate as DateTime) + #count) - (
CASE SIGN (MONTH (DOB) - MONTH (cast(#CalDate as DateTime) + #count))
WHEN 1 THEN
1
WHEN -1 THEN
0
WHEN 0 THEN
CASE SIGN (DAY (DOB) - DAY (#CalDate + #count))
WHEN 1 THEN
1
WHEN 0 THEN
1
ELSE
0
END
END) as AGE into #temp
FROM test_db.dbo.ip_master ip_master
select * from #temp where AGE >= 65

Whatever you have done is correct.
For singling out you need a where clause.
SELECT ip_master.ssn, ip_master.firstname, ip_master.surname, ip_master.status,
CASE WHEN DATEADD(YEAR, DATEDIFF (YEAR, dob, '2013/03/31'), dob) > '2013/03/31'
THEN DATEDIFF(YEAR, dob, '2013/03/31') - 1
ELSE DATEDIFF(YEAR, dob, '2013/03/31')
END AS 'Age'
FROM test_db.dbo.ip_master ip_master
WHERE dob = '1948-03-31'

Calculate age of a person in SQL [duplicate]

This question already has answers here:
Closed 11 years ago.
Possible Duplicate:
How to calculate age in T-SQL with years, months, and days
It seems like something simple, but it doesn't seem to work for me. I want to calculate the age of someone base on two dates in SQL.
I did DATEDIFF(year,Birthdate,ReferenceDate) and it doesn't always give me the right age.
For example
DATEDIFF(year,'1981-07-05',2011-07-01')
gives 30, while it should still be 29. Is there a way to do this ?
Thanks,

Try this...
SELECT CASE WHEN
(DATEADD(year,DATEDIFF(year, #datestart ,#dateend) , #datestart) > #dateend)
THEN DATEDIFF(year, #datestart ,#dateend) -1
ELSE DATEDIFF(year, #datestart ,#dateend)
END
It just compares the year difference and if it is greater then subtracts a year, else it returns the value.

Declare #Date1 datetime
Declare #Date2 datetime
Select #Date1 = '07/25/1984'
Select #Date2 = GetDate()
select CASE
WHEN dateadd(year, datediff (year, #Date1, #Date2), #Date1) > #Date2
THEN datediff (year, #Date1, #Date2) - 1
ELSE datediff (year, #Date1, #Date2)END as Age

Try This
select
(datediff(yy,'1981-07-08',getdate()))-(datepart(yy,(convert(datetime,convert(int,dateadd(yy,datediff(yy,'1981-07-08',getdate()),'1981-07-08'))-convert(int,dateadd(yy,-1,getdate())))))-1900)