Date Value from a week number in SQL [duplicate] - sql

This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
Get dates from a week number in T-SQL
How do I get the date value if I have a week number in SQL Query.
Like if I pass 26, it should give me 06/24/2012. If I pass 27, I should get 07/01/2012
Any help will be appreciated :)
Sots

SELECT DATEADD(week, n, '11/25/2011');
with n being the week number

If this doesn't work, try using WEEK() instead of WEEKOFYEAR().
CURDATE() - INTERVAL WEEKDAY(CURDATE()) DAY + INTERVAL (WEEKNO - WEEKOFYEAR(CURDATE())) WEEK

In SQL Server
DECLARE #StartDate DATE, #WeekVal INT
SET #WeekVal = 26 -- Set the week number
SET #StartDate = DATEADD(YEAR, DATEDIFF(YEAR, 0, GETDATE()), 0) -- Start of current year
;WITH cte AS (
SELECT #StartDate AS DateVal, DATEPART(wk, #StartDate) AS WeekVal, 1 AS RowVal
UNION ALL
SELECT DATEADD(d, 1, DateVal), DATEPART(wk, DATEADD(d, 1, DateVal)), RowVal + 1
FROM cte WHERE RowVal < 365
)
SELECT MIN(DateVal) StartOfWeek
FROM cte
WHERE WeekVal = #WeekVal
OPTION (MAXRECURSION 365);

This gives you the start and end dates of the week. [For SQL Server]
Declare #week integer set #week = 26
Declare #Year Integer Set #Year = year(getdate())
declare #date datetime
-- ------------------------------------
Set #date = DateAdd(day, 0,
DateAdd(month, 0,
DateAdd(Year, #Year-1900, 0)))
set #date = Dateadd(week, #week-1, #date)
select #date startweek, DATEADD (D, -1 * DatePart (DW, #date) + 7, #date) endweek
This was the result from it:
startweek endweek
----------------------- -----------------------
2012-07-01 00:00:00.000 2012-07-07 00:00:00.000
(1 row(s) affected)

Related

get all date in current month and last month in sql [duplicate]

This question already has answers here:
Get a list of dates between two dates using a function
(21 answers)
Closed 5 years ago.
I would like to get all dates in a current month and last month from today.like, if today is 24/02/2017 and i want to get dates like 24/02/2017,23/02/2017,22/02/2107-- to 23-01-2017 in SQL Server.
use Recursive cte
with cte as
(
select getdate() as n
union all
select dateadd(DAY,-1,n) from cte where dateadd(dd,-1,n)> DATEADD(month, -1, getdate())
)
select * from cte
A simple WHILE will do the trick
declare
#today date = getdate()
,#day date
set #day = #today
while #day >= DATEADD(month, -1, #today)
begin
select #day
set #day = DATEADD(day, -1, #day)
end
If you want it in a table just insert in a temp table this way. Also code corrected to iterate until today -1 day -1 month like in your example.
declare
#today date = getdate()
,#day date
declare
#daysTable table ([day] date not null)
set #day = #today
while #day >= DATEADD(DAY, -1, DATEADD(month, -1, #today))
begin
--select #day
insert into #daysTable values (#day)
set #day = DATEADD(day, -1, #day)
end
select * from #daysTable

Finding week start and week end date

I have a week number and year and i need to display "total for mm/dd/yy to mm/dd/yy in a row of my ssrs report. My week starts with Monday. For example if my week number is '2' and year is '2010' then I have to display "total for 01/04/2010 to 01/10/2010 in my ssrs column. how to do this?
Try this
declare #year char(4) = '2010'
declare #week int = 2
declare #fromdate datetime
declare #todate datetime
set #fromdate = DATEADD(wk, DATEDIFF(wk, 6, '1/1/' + #year) + (#week-1), 7);
set #todate = DATEADD(wk, DATEDIFF(wk, 5, '1/1/' + #year) + (#week-1), 6) ;
;WITH dates AS
(
SELECT CONVERT(datetime,#fromDate) as Date
UNION ALL
SELECT DATEADD(d,1,[Date])
FROM dates
WHERE DATE < #toDate
)
select * from dates
SQL Server has a DATEPART function which calculates the ordinal week number of a year. However, you have to call DATEFIRST before this to define which day of the week represents the start of the week. In your case, you have stated that the start of your week is Monday (i.e. 1).
SET DATEFIRST 1;
SELECT SUM([your data column])
FROM [your table]
WHERE DATEPART(WEEKNUM, [your date column])=[your week parameter]
AND DATEPART(YEAR, [your date column])=[your year parameter]
Your description is not american standard nor isoweek. Seems like a mix of those. I never heard of that as a standard. It is nearly isoweek. So that is what this answer is based on.
Calculating iso year is a bit tricky, you can read about it here:
This is the syntax you need:
DECLARE #year int = 2010
DECLARE #week int = 2
;WITH CTE AS
(
SELECT
dateadd(wk, datediff(wk, - #week * 7,
cast(cast(#year as char(4)) as datetime) - 5), 0) startofweek
)
SELECT
replace('total for ' + convert(char(10), startofweek, 110)
+ ' to ' + convert(char(10), dateadd(day, 6, startofweek) , 110), '-', '/')
FROM CTE
Result:
total for 01/11/2010 to 01/17/2010
Isoweek 2 in 2010 is 2010-01-11
Try setting DATEFIRST (https://msdn.microsoft.com/en-ie/library/ms181598.aspx)
SET DATEFIRST 7
declare #wk int
declare #yr int
declare #EndOfWeek as datetime
set #wk = 2
set #yr = 2010
SET #EndOfWeek = dateadd (week, #wk, dateadd (year, #yr-1900, 0)) + 1 - datepart(dw, dateadd (week, #wk, dateadd (year, #yr-1900, 0)) )
SELECT
replace('total for ' + convert(char(10), dateadd(day, -6, #EndOfWeek) , 110)
+ ' to ' + convert(char(10), #EndOfWeek, 110), '-', '/')
The result:
total for 01/04/2010 to 01/10/2010
I hope it helps:
declare #year char(4) = '2014'
declare #week int = 2
select dateadd(week,#week,convert(date,#year+'-01-01',121))
Change the date format appropriate for you from this list

(Transact-SQL) DATEDIFF and leap years

I have a problem with DATEDIFF function.
My date format is dd/mm/yyyy.
#START_DATE = 01/02/2004
#END_DATE = 29/01/2014
The query (DATEDIFF(DAY,#START_DATE,#END_DATE) / 365) return 10, but the number of correct years is 9. This happens because my query does not consider leap years.
What I can do to keep an accurate count?
Thanks.
I believe the following logic does what you want:
datediff(year,
#START_DATE - datepart(dayofyear, #START_DATE) + 1,
#END_DATE - datepart(dayofyear, #START_DATE) + 1
) as d2
Note: This treats that dates as datetime, because arithmetic is easier to express. You can also write this as:
datediff(year,
dateadd(day, - datepart(dayofyear, #START_DATE) + 1, #START_DATE),
dateadd(day, - datepart(dayofyear, #START_DATE) + 1, #END_DATE)
) as d2
The following query is a demonstration:
select datediff(year,
startdate - datepart(dayofyear, startdate) + 1,
enddate - datepart(dayofyear, startdate) + 1
) as d2
from (select cast('2004-02-01' as datetime) as startdate,
cast('2014-01-31' as datetime) as enddate
union all
select cast('2004-02-01' as datetime) as startdate,
cast('2014-02-01' as datetime) as enddate
) t
Technically there would be 365.242 days in a year, when accounting for leap years so:
FLOOR(DATEDIFF(day, #STARTDATE, #ENDDATE) / 365.242)
Should be more correct.
Test:
SELECT FLOOR(DATEDIFF(day, '1980-01-16','2015-01-15') / 365.242),
FLOOR(DATEDIFF(day, '1980-01-16','2015-01-16') / 365.242)
ResultSet:
--------------------------------------- ---------------------------------------
34 35
Cheers!
You can create a function to address that:
CREATE FUNCTION [dbo].[getYears]
(
#START_DATE datetime,
#END_DATE datetime
)
RETURNS int
AS
BEGIN
DECLARE #yrs int
SET #yrs =DATEDIFF(year,#START_DATE,#END_DATE)
IF (#END_DATE < DATEADD(year, #yrs, #START_DATE))
SET #yrs = #yrs -1
RETURN #yrs
END
Also check this
Count the number of leap days in end_date Deduct number of leap days in start_date. Deduct the answer from your DATEDIFF.
DECLARE
#START_DATE DATETIME = '2004-02-01',
#END_DATE DATETIME = '2014-01-29'
SELECT (
DATEDIFF(DAY,#START_DATE,#END_DATE)
- (
(CONVERT(INT,#END_DATE - 58) / 1461)
-
(CONVERT(INT,#START_DATE - 58) / 1461)
)
) / 365
-58 to ignore Jan and Feb 1900
/ 1461 being the number of days between leap years

How to get Saturday's Date (Or any other weekday's Date)- SQL Server

How to get Saturday's Date. I have today's date with me.
GETDATE()
How to do this.
For eg. TODAY is 08-08-2011
I want output as 08-13-2011
This is a function that will return the next Saturday if you call it like this:
SELECT dbo.fn_Get_NextWeekDay('2011-08-08', 6)
The "6" comes from the list of possible values you can set for DATEFIRST.
You can get any other day of the week by changing the second parameter accordingly.
This is the function:
IF OBJECT_ID('dbo.fn_Get_NextWeekDay') IS NOT NULL
DROP FUNCTION dbo.fn_Get_NextWeekDay
GO
CREATE FUNCTION dbo.fn_Get_NextWeekDay(
#aDate DATETIME
, #dayofweek INT
/*
#dw - day of the week
1 - Monday
2 - Tuesday
3 - Wednesday
4 - Thursday
5 - Friday
6 - Saturday
7 - Sunday
*/
)
RETURNS DATETIME
AS
/*
SELECT dbo.fn_Get_NextWeekDay('2011-08-08', 6)
SELECT dbo.fn_Get_NextWeekDay('2011-08-08', 1)
*/
BEGIN
RETURN
DATEADD(day
, ( #dayofweek + 8 - DATEPART(dw, #aDate) - ##DATEFIRST ) % 7
, #aDate
)
END
GO
[EDIT]
This might be another solution. This should work in any language:
IF OBJECT_ID('dbo.fn_NextWeekDay') IS NOT NULL
DROP FUNCTION dbo.fn_NextWeekDay
GO
CREATE FUNCTION dbo.fn_NextWeekDay(
#aDate DATE
, #dayofweek NVARCHAR(30)
)
RETURNS DATE
AS
/*
SELECT dbo.fn_NextWeekDay('2016-12-14', 'fri')
SELECT dbo.fn_NextWeekDay('2016-03-15', 'mon')
*/
BEGIN
DECLARE #dx INT = 6
WHILE UPPER(DATENAME(weekday,#aDate)) NOT LIKE UPPER(#dayofweek) + '%'
BEGIN
SET #aDate = DATEADD(day,1,#aDate)
SET #dx=#dx-1
if #dx < 0
BEGIN
SET #aDate = NULL
BREAK
END
END
RETURN #aDate
END
GO
Use DATEPART to get the day of week of today and add the difference to the desired day of week to todays date.
DECLARE #Today date = 'TODAYS-DATE';
DECLARE #TodayNumber int = DATEPART(dw, #Today) -- Get the day number
DECLARE #Saturday date = DATEADD(DAY, (6-#TodayNumber)%7, #Today)
-- Add the number of days between today and saturday (the 6th day), modulus 7 to stop you adding negative days
Hope that helps!
Use a Calendar table (table with one row per date):
SELECT MIN(DateValue) DateValue
FROM Calendar
WHERE DateValue >= CURRENT_TIMESTAMP
AND DayOfWeek = 'Saturday';
Another approach to this takes two steps, but might be more readable (look ma, no modulus):
Go back to last saturday: DATEADD(DAY, -1 * datepart(weekday, GETDATE()), getdate())
Then, add on a week: DATEADD(WEEK, 1, #lastSaturday, getdate()))
The whole thing:
declare #today DATETIME = GETDATE()
declare #lastSaturday DATETIME = DATEADD(DAY, -1 * datepart(weekday, #today), #today)
declare #nextSaturday DATETIME = DATEADD(WEEK, 1, #lastSaturday)
Or, if you're ok with #today being GETDATE(), you can do the calculation all at once:
SELECT DATEADD(WEEK, 1, DATEADD(DAY, -1 * datepart(weekday, GETDATE()), getdate()))
Checkout the SQL DATEADD function.
DATEADD (Transact-SQL)
Which you can use this along with DATEPART function to return the correct date.
DATEPART (Transact-SQL)
Try this :
SET DATEFIRST 7
DECLARE #d DATETIME
SET #d = '2011-08-08' --GETDATE()
SELECT NEXT_SAT = DATEADD(day, (7 + ##DATEFIRST - DATEPART(dw, #d)) % 7, #d )
declare #Curdate date=( SELECT SWITCHOFFSET(SYSDATETIMEOFFSET(),'+05:30') )
declare #nextsaturdaydate date=(select dateadd(d, 7-datepart(WEEKDAY, #CurDate),#Curdate))
select #nextsaturdaydate

How to determine the number of days in a month in SQL Server?

I need to determine the number of days in a month for a given date in SQL Server.
Is there a built-in function? If not, what should I use as the user-defined function?
In SQL Server 2012 you can use EOMONTH (Transact-SQL) to get the last day of the month and then you can use DAY (Transact-SQL) to get the number of days in the month.
DECLARE #ADate DATETIME
SET #ADate = GETDATE()
SELECT DAY(EOMONTH(#ADate)) AS DaysInMonth
You can use the following with the first day of the specified month:
datediff(day, #date, dateadd(month, 1, #date))
To make it work for every date:
datediff(day, dateadd(day, 1-day(#date), #date),
dateadd(month, 1, dateadd(day, 1-day(#date), #date)))
Most elegant solution: works for any #DATE
DAY(DATEADD(DD,-1,DATEADD(MM,DATEDIFF(MM,-1,#DATE),0)))
Throw it in a function or just use it inline. This answers the original question without all the extra junk in the other answers.
examples for dates from other answers:
SELECT DAY(DATEADD(DD,-1,DATEADD(MM,DATEDIFF(MM,-1,'1/31/2009'),0))) Returns 31
SELECT DAY(DATEADD(DD,-1,DATEADD(MM,DATEDIFF(MM,-1,'2404-feb-15'),0))) Returns 29
SELECT DAY(DATEADD(DD,-1,DATEADD(MM,DATEDIFF(MM,-1,'2011-12-22'),0))) Returns 31
--Last Day of Previous Month
SELECT DATEPART(day, DATEADD(s,-1,DATEADD(mm, DATEDIFF(m,0,GETDATE()),0)))
--Last Day of Current Month
SELECT DATEPART(day, DATEADD(s,-1,DATEADD(mm, DATEDIFF(m,0,GETDATE())+1,0)))
--Last Day of Next Month
SELECT DATEPART(day, DATEADD(s,-1,DATEADD(mm, DATEDIFF(m,0,GETDATE())+2,0)))
Personally though, I would make a UDF for it if there is not a built in function...
I would suggest:
SELECT DAY(EOMONTH(GETDATE()))
This code gets you the number of days in current month:
SELECT datediff(dd,getdate(),dateadd(mm,1,getdate())) as datas
Change getdate() to the date you need to count days for.
--- sql server below 2012---
select day( dateadd(day,-1,dateadd(month, 1, convert(date,'2019-03-01'))))
-- this for sql server 2012--
select day(EOMONTH(getdate()))
Solution 1: Find the number of days in whatever month we're currently in
DECLARE #dt datetime
SET #dt = getdate()
SELECT #dt AS [DateTime],
DAY(DATEADD(mm, DATEDIFF(mm, -1, #dt), -1)) AS [Days in Month]
Solution 2: Find the number of days in a given month-year combo
DECLARE #y int, #m int
SET #y = 2012
SET #m = 2
SELECT #y AS [Year],
#m AS [Month],
DATEDIFF(DAY,
DATEADD(DAY, 0, DATEADD(m, ((#y - 1900) * 12) + #m - 1, 0)),
DATEADD(DAY, 0, DATEADD(m, ((#y - 1900) * 12) + #m, 0))
) AS [Days in Month]
You do need to add a function, but it's a simple one. I use this:
CREATE FUNCTION [dbo].[ufn_GetDaysInMonth] ( #pDate DATETIME )
RETURNS INT
AS
BEGIN
SET #pDate = CONVERT(VARCHAR(10), #pDate, 101)
SET #pDate = #pDate - DAY(#pDate) + 1
RETURN DATEDIFF(DD, #pDate, DATEADD(MM, 1, #pDate))
END
GO
SELECT Datediff(day,
(Convert(DateTime,Convert(varchar(2),Month(getdate()))+'/01/'+Convert(varchar(4),Year(getdate())))),
(Convert(DateTime,Convert(varchar(2),Month(getdate())+1)+'/01/'+Convert(varchar(4),Year(getdate()))))) as [No.of Days in a Month]
select datediff(day,
dateadd(day, 0, dateadd(month, ((2013 - 1900) * 12) + 3 - 1, 0)),
dateadd(day, 0, dateadd(month, ((2013 - 1900) * 12) + 3, 0))
)
Nice Simple and does not require creating any functions Work Fine
You need to create a function, but it is for your own convenience. It works perfect and I never encountered any faulty computations using this function.
CREATE FUNCTION [dbo].[get_days](#date datetime)
RETURNS int
AS
BEGIN
SET #date = DATEADD(MONTH, 1, #date)
DECLARE #result int = (select DAY(DATEADD(DAY, -DAY(#date), #date)))
RETURN #result
END
How it works: subtracting the date's day number from the date itself gives you the last day of previous month. So, you need to add one month to the given date, subtract the day number and get the day component of the result.
select add_months(trunc(sysdate,'MM'),1) - trunc(sysdate,'MM') from dual;
I upvoted Mehrdad, but this works as well. :)
CREATE function dbo.IsLeapYear
(
#TestYear int
)
RETURNS bit
AS
BEGIN
declare #Result bit
set #Result =
cast(
case when ((#TestYear % 4 = 0) and (#testYear % 100 != 0)) or (#TestYear % 400 = 0)
then 1
else 0
end
as bit )
return #Result
END
GO
CREATE FUNCTION dbo.GetDaysInMonth
(
#TestDT datetime
)
RETURNS INT
AS
BEGIN
DECLARE #Result int
DECLARE #MonthNo int
Set #MonthNo = datepart(m,#TestDT)
Set #Result =
case #MonthNo
when 1 then 31
when 2 then
case
when dbo.IsLeapYear(datepart(yyyy,#TestDT)) = 0
then 28
else 29
end
when 3 then 31
when 4 then 30
when 5 then 31
when 6 then 30
when 7 then 31
when 8 then 31
when 9 then 30
when 10 then 31
when 11 then 30
when 12 then 31
end
RETURN #Result
END
GO
To Test
declare #testDT datetime;
set #testDT = '2404-feb-15';
select dbo.GetDaysInMonth(#testDT)
here's another one...
Select Day(DateAdd(day, -Day(DateAdd(month, 1, getdate())),
DateAdd(month, 1, getdate())))
I know this question is old but I thought I would share what I'm using.
DECLARE #date date = '2011-12-22'
/* FindFirstDayOfMonth - Find the first date of any month */
-- Replace the day part with -01
DECLARE #firstDayOfMonth date = CAST( CAST(YEAR(#date) AS varchar(4)) + '-' +
CAST(MONTH(#date) AS varchar(2)) + '-01' AS date)
SELECT #firstDayOfMonth
and
DECLARE #date date = '2011-12-22'
/* FindLastDayOfMonth - Find what is the last day of a month - Leap year is handled by DATEADD */
-- Get the first day of next month and remove a day from it using DATEADD
DECLARE #lastDayOfMonth date = CAST( DATEADD(dd, -1, DATEADD(mm, 1, FindFirstDayOfMonth(#date))) AS date)
SELECT #lastDayOfMonth
Those could be combine to create a single function to retrieve the number of days in a month if needed.
SELECT DAY(SUBDATE(ADDDATE(CONCAT(YEAR(NOW()), '-', MONTH(NOW()), '-1'), INTERVAL 1 MONTH), INTERVAL 1 DAY))
Nice 'n' Simple and does not require creating any functions
Mehrdad Afshari reply is most accurate one, apart from usual this answer is based on formal mathematical approach given by Curtis McEnroe in his blog https://cmcenroe.me/2014/12/05/days-in-month-formula.html
DECLARE #date DATE= '2015-02-01'
DECLARE #monthNumber TINYINT
DECLARE #dayCount TINYINT
SET #monthNumber = DATEPART(MONTH,#date )
SET #dayCount = 28 + (#monthNumber + floor(#monthNumber/8)) % 2 + 2 % #monthNumber + 2 * floor(1/#monthNumber)
SELECT #dayCount + CASE WHEN #dayCount = 28 AND DATEPART(YEAR,#date)%4 =0 THEN 1 ELSE 0 END -- leap year adjustment
To get the no. of days in a month we can directly use Day() available in SQL.
Follow the link posted at the end of my answer for SQL Server 2005 / 2008.
The following example and the result are from SQL 2012
alter function dbo.[daysinm]
(
#dates nvarchar(12)
)
returns int
as
begin
Declare #dates2 nvarchar(12)
Declare #days int
begin
select #dates2 = (select DAY(EOMONTH(convert(datetime,#dates,103))))
set #days = convert(int,#dates2)
end
return #days
end
--select dbo.daysinm('08/12/2016')
Result in SQL Server SSMS
(no column name)
1 31
Process:
When EOMONTH is used, whichever the date format we use it is converted into DateTime format of SQL-server. Then the date output of EOMONTH() will be 2016-12-31 having 2016 as Year, 12 as Month and 31 as Days.
This output when passed into Day() it gives you the total days count in the month.
If we want to get the instant result for checking we can directly run the below code,
select DAY(EOMONTH(convert(datetime,'08/12/2016',103)))
or
select DAY(EOMONTH(convert(datetime,getdate(),103)))
for reference to work in SQL Server 2005/2008/2012, please follow the following external link ...
Find No. of Days in a Month in SQL
DECLARE #date DATETIME = GETDATE(); --or '12/1/2018' (month/day/year)
SELECT DAY(EOMONTH ( #date )) AS 'This Month';
SELECT DAY(EOMONTH ( #date, 1 )) AS 'Next Month';
result:
This Month
31
Next Month
30
DECLARE #m int
SET #m = 2
SELECT
#m AS [Month],
DATEDIFF(DAY,
DATEADD(DAY, 0, DATEADD(m, +#m -1, 0)),
DATEADD(DAY, 0, DATEADD(m,+ #m, 0))
) AS [Days in Month]
RETURN day(dateadd(month, 12 * #year + #month - 22800, -1))
select day(dateadd(month, 12 * year(date) + month(date) - 22800, -1))
A cleaner way of implementing this is using the datefromparts function to construct the first day of the month, and calculate the days from there.
CREATE FUNCTION [dbo].[fn_DaysInMonth]
(
#year INT,
#month INT
)
RETURNS INT
AS
BEGIN
IF #month < 1 OR #month > 12 RETURN NULL;
IF #year < 1753 OR #year > 9998 RETURN NULL;
DECLARE #firstDay DATE = datefromparts(#year, #month, 1);
DECLARE #lastDay DATE = dateadd(month, 1, #firstDay);
RETURN datediff(day, #firstDay, #lastDay);
END
GO
Similarily, you can calculate the days in a year:
CREATE FUNCTION [dbo].[fn_DaysInYear]
(
#year INT
)
RETURNS INT
AS
BEGIN
IF #year < 1753 OR #year > 9998 RETURN NULL;
DECLARE #firstDay DATE = datefromparts(#year, 1, 1);
DECLARE #lastDay DATE = dateadd(year, 1, #firstDay);
RETURN datediff(day, #firstDay, #lastDay);
END
GO
use SQL Server EOMONTH Function nested with day to get last day of month
select Day(EOMONTH('2020-02-1')) -- Leap Year returns 29
select Day(EOMONTH('2021-02-1')) -- returns 28
select Day(EOMONTH('2021-03-1')) -- returns 31
For any date
select DateDiff(Day,#date,DateAdd(month,1,#date))
select first_day=dateadd(dd,-1*datepart(dd,getdate())+1,getdate()),
last_day=dateadd(dd,-1*datepart(dd,dateadd(mm,1,getdate())),dateadd(mm,1,getdate())),
no_of_days = 1+datediff(dd,dateadd(dd,-1*datepart(dd,getdate())+1,getdate()),dateadd(dd,-1*datepart(dd,dateadd(mm,1,getdate())),dateadd(mm,1,getdate())))
replace any date with getdate to get the no of months in that particular date
DECLARE #Month INT=2,
#Year INT=1989
DECLARE #date DateTime=null
SET #date=CAST(CAST(#Year AS nvarchar) + '-' + CAST(#Month AS nvarchar) + '-' + '1' AS DATETIME);
DECLARE #noofDays TINYINT
DECLARE #CountForDate TINYINT
SET #noofDays = DATEPART(MONTH,#date )
SET #CountForDate = 28 + (#noofDays + floor(#noofDays/8)) % 2 + 2 % #noofDays + 2 * floor(1/#noofDays)
SET #noofDays= #CountForDate + CASE WHEN #CountForDate = 28 AND DATEPART(YEAR,#date)%4 =0 THEN 1 ELSE 0 END
PRINT #noofDays
DECLARE #date nvarchar(20)
SET #date ='2012-02-09 00:00:00'
SELECT DATEDIFF(day,cast(replace(cast(YEAR(#date) as char)+'-'+cast(MONTH(#date) as char)+'-01',' ','')+' 00:00:00' as datetime),dateadd(month,1,cast(replace(cast(YEAR(#date) as char)+'-'+cast(MONTH(#date) as char)+'-01',' ','')+' 00:00:00' as datetime)))
simple query in SQLServer2012 :
select day(('20-05-1951 22:00:00'))
i tested for many dates and it return always a correct result