The SQL Server helper function to format datetime values.

create function dbo.FormatDateTime(
    @DateFormat varchar(50),
    @Date datetime
)

/*------------------------------------------------------------------------------

Converts different datetime formats and relavant date parts.

usage

    select dbo.FormatDateTime('YYYY-MM-DD',getdate());
    select dbo.FormatDateTime('LASTDAY DDDD',getdate());
    select dbo.FormatDateTime('Dayofyear', GETDATE()+200);
    select dbo.FormatDateTime('LASTDAY DDDD', GETDATE()+245);
    select dbo.FormatDateTime('YYYY-MM-DD', GETDATE()+245);

Parameters                      |   Result
________________________________________________________________________
dd-mmm-yyyy                     |   22-OCT-2008
MMM DD YYYY HH-mm Am/pm         |   Oct 22 2008  6-02AM
MM/DD/YYYY                      |   10/22/2008
YYYY.MM.DD                      |   2008.10.22
DD/MM/YYYY                      |   22/10/2008
DD.MM.YYYY                      |   22.10.2008
DD/MM/YYYY                      |   22/10.2008
DD-MM-YYYY                      |   22-10-2008
DD MMM YYYY                     |   22 Oct 2008
MMM DD,YYYY                     |   Oct 22, 2008
HH-mm-SS                        |   06-33-22
MMM DD YYYY H-mm-SS-MSAM/PM     |   Oct 22 2008  6-12-30-540AM
DD-MM-YYYY                      |   22-10-2008
YYYY/MM/DD                      |   2008/10/22
YYYYMMDD                        |   20081022
DD MMM YYYY HH-mm-SS-MS         |   Oct 22 2008  6-12-30-540AM (will actually by colon, but we can use here since install cd breaks)
HH-mm-SS-MS                     |   06-18-30-740
Julion                          |   39741
Day                             |   22
Month                           |   10
Year                            |   2008
YYYY-MM                         |   2008-10
MM-YYYY                         |   10-2008
YYYY MM                         |   2008 10
MM YYYY                         |   10 2008
Week                            |   43 week in year
Dayofyear                       |   293 day in year
quarter                         |   4 Year Quarter
Weekday                         |   4 day number of week
MMMM                            |   October
DDDD                            |   Wednesday
DDDD DD MMMM YYYY               |   Wednesday 22 October 2008
DDDD MMMM YYYY                  |   Wednesday  October 2008
LASTDAY                         |   2008/10/31 (last day of month)
LASTDAY DDDD                    |   Friday (last day of month)
YYYY-MM-DD                      |   2008-11-11
-----------------------------------------------------------------------------*/

returns varchar(30)
as
begin
    declare @myRes varchar(25);

    if @DateFormat = 'dd-mmm-yyyy'
        begin
            set @myRes = Cast(day(@Date) as varchar(2))+'-'+substring(datename(m, @Date), 1, 3)+'-'+cast(year(@Date) as varchar(4));
        end;

    -- 'Returns the date MMM DD YYYY HH:mm Am/pm'
    -- 'EG Oct 22 2008  6:02AM'
    if @DateFormat = 'MMM DD YYYY HH:mm Am/pm'
        begin
            set @myRes = CONVERT(varchar(30), @Date, 100);
        end;

    -- Returns the date MM/DD/YYYY
    -- EG 10/22/2008
    if @DateFormat = 'MM/DD/YYYY'
        begin
            set @myRes = CONVERT(varchar(30), @Date, 101);
        end;
    -- Returns the date YYYY.MM.DD
    -- EG 2008.10.22
    if @DateFormat = 'YYYY.MM.DD'
        begin
            set @myRes = CONVERT(varchar(30), @Date, 102);
        end;
    -- Returns the date DD/MM/YYYY
    -- EG 22/10/2008
    if @DateFormat = 'DD/MM/YYYY'
        begin
            set @myRes = CONVERT(varchar(30), @Date, 103);
        end;
    -- Returns the date DD.MM.YYYY
    -- EG 22.10.2008
    if @DateFormat = 'DD.MM.YYYY'
        begin
            set @myRes = CONVERT(varchar(30), @Date, 104);
        end;

    -- Returns the date DD-MM-YYYY
    -- EG 22-10-2008
    if @DateFormat = 'DD-MM-YYYY'
        begin
            set @myRes = CONVERT(varchar(30), @Date, 105);
        end;
    -- Returns the date DD MMM YYYY
    -- EG 22 Oct 2008
    if @DateFormat = 'DD MMM YYYY'
        begin
            set @myRes = CONVERT(varchar(30), @Date, 106);
        end;
    -- Returns the date DD MMM YYYY
    -- EG Oct 22, 2008
    if @DateFormat = 'MMM DD,YYYY'
        begin
            set @myRes = CONVERT(varchar(30), @Date, 107);
        end;

    -- 'Returns the time HH:mm:SS'
    -- 'EG  06:11:24'
    if @DateFormat = 'HH:mm:SS'
        begin

            set @myRes = CONVERT(varchar(30), @Date, 108);
        end;

    -- 'Returns the Date MMM DD YYYY H:mm:SS:MSAM/PM'
    -- 'EG  Oct 22 2008  6:12:30:540AM'
    if @DateFormat = 'MMM DD YYYY H:mm:SS:MSAM/PM'
        begin
            set @myRes = CONVERT(varchar(30), @Date, 109);
        end;

    -- Returns the Date DD-MM-YYYY
    -- EG  10-22-2008
    if @DateFormat = 'DD-MM-YYYY'
        begin
            set @myRes = CONVERT(varchar(30), @Date, 110);
        end;

    -- Returns the Date YYYY/MM/DD
    -- EG  2008/10/22
    if @DateFormat = 'YYYY/MM/DD'
        begin
            set @myRes = CONVERT(varchar(30), @Date, 111);
        end;

    -- Returns the Date YYYYMMDD
    -- EG  20081022
    if @DateFormat = 'YYYYMMDD'
        begin
            set @myRes = CONVERT(varchar(30), @Date, 112);
        end;

    -- 'Returns the Date DD MMM YYYY HH:mm:SS:MS'
    -- 'EG  22 Oct 2008 06:17:18:883'
    if @DateFormat = 'DD MMM YYYY HH:mm:SS:MS'
        begin
            set @myRes = CONVERT(varchar(30), @Date, 113);
        end;

    -- 'Returns the time  HH:mm:SS:MS'
    -- 'EG  06:18:30:740'
    if @DateFormat = 'HH:mm:SS:MS'
        begin
            set @myRes = CONVERT(varchar(30), @Date, 114);
        end;

    -- Returns the Date Julion
    -- EG  2008-10-22 is represented as 39741
    if @DateFormat = 'Julion'
        begin
            set @myRes = CONVERT(varchar(30), DATEDIFF(day, CONVERT(datetime, '1900-01-01', 110), @Date));
        end;

    -- Returns the Day
    -- EG  2008-10-22 is represented as 22
    if @DateFormat = 'Day'
        begin
            set @myRes = CONVERT(varchar(30), DAY(@Date));
        end;

    -- Returns the Month
    -- EG  2008-10-22 is represented as 10
    if @DateFormat = 'Month'
        begin
            set @myRes = CONVERT(varchar(30), Month(@Date));
        end;

    -- Returns the year
    -- EG  2008-10-22 is represented as 2008
    if @DateFormat = 'Year'
        begin
            set @myRes = CONVERT(varchar(30), Year(@Date));
        end;

    -- Returns the date in YYYY-MM
    -- EG  2008-10-22 is represented as 2008-10
    if @DateFormat = 'YYYY-MM'
        begin
            set @myRes = CONVERT(varchar(30), Year(@Date))+'-'+CONVERT(varchar(30), Month(@Date));
        end;

    -- Returns the date in MM-YYYY
    -- EG  2008-10-22 is represented as 10-2008
    if @DateFormat = 'MM-YYYY'
        begin
            set @myRes = CONVERT(varchar(30), Month(@Date))+'-'+CONVERT(varchar(30), Year(@Date));
        end;

    -- Returns the date in YYYY MM
    -- EG  2008-10-22 is represented as 2008-10
    if @DateFormat = 'YYYY MM'
        begin
            set @myRes = CONVERT(varchar(30), Year(@Date))+' '+CONVERT(varchar(30), Month(@Date));
        end;

    -- Returns the date in MM YYYY
    -- EG  2008-10-22 is represented as 10 2008
    if @DateFormat = 'MM YYYY'
        begin
            set @myRes = CONVERT(varchar(30), Month(@Date))+' '+CONVERT(varchar(30), Year(@Date));
        end;

    -- Returns the date in WeekNo
    -- EG  2008-10-22 is represented as week 43
    if @DateFormat = 'Week'
        begin
            set @myRes = CONVERT(varchar(30), DATEPART(wk, @Date));
        end;

    -- Returns the date in Dayofyear
    -- EG  2008-10-22 is represented as 296
    if @DateFormat = 'Dayofyear'
        begin
            set @myRes = CONVERT(varchar(30), DATEPART(dy, @Date));
        end;
    -- Returns the Quarter of the year
    -- EG  2008-10-22 is represented as week 4
    if @DateFormat = 'quarter'
        begin
            set @myRes = CONVERT(varchar(30), DATEPART(qq, @Date));
        end;

    -- Returns the day of the week starting on Sunday as day 1
    -- EG  2008-10-22 is represented as day 4
    if @DateFormat = 'Weekday'
        begin
            set @myRes = CONVERT(varchar(30), DATEPART(dw, @Date));
        end;

    -- Returns the day of the long Month name format
    -- EG  2008-10-22 is represented as day OCtober
    if @DateFormat = 'MMMM'
        begin
            set @myRes = CONVERT(varchar(30), DAteNAME(month, @Date));
        end;

    -- Returns the day of the long Month name format
    -- EG  2008-10-22 is represented as  Wednesday
    if @DateFormat = 'DDDD'
        begin
            set @myRes = CONVERT(varchar(30), DAteNAME(weekday, @Date));
        end;

    -- Returns the day of the long Month name format
    -- EG  2008-10-22 is represented as  22 OCtober  2008
    if @DateFormat = 'DDDD DD MMMM YYYY'
        begin
            set @myRes = DATENAME(weekday, @Date)+' '+CONVERT(varchar(30), DAtEPART(DAY, @Date))+' '+CONVERT(varchar(30), DAteNAME(month, @Date))+' '+CONVERT(varchar(30), DAtEPART(YEAR, @Date));
        end;
    -- Returns the day of the long Month name format
    -- EG  2008-10-22 is represented as 22 OCtober  2008
    if @DateFormat = 'DD MMMM YYYY'
        begin
            set @myRes = CONVERT(varchar(30), DAtEPART(DAY, @Date))+' '+CONVERT(varchar(30), DAteNAME(month, @Date))+' '+CONVERT(varchar(30), DAtEPART(YEAR, @Date));
        end;

    -- Returns the day of the last Day of month
    -- EG  2008-10-22 is represented as 2008/10/31
    if @DateFormat = 'LASTDAY'
        begin
            set @myRes = CONVERT(varchar(30), dateadd(day, -1 * day(dateadd(month, 1, @Date)), dateadd(month, 1, @Date)), 111);
        end;

    -- Returns the day of the last Day of month
    -- EG  2008-10-22 is represented as Friday
    if @DateFormat = 'LASTDAY DDDD'
        begin
            set @myRes = CONVERT(varchar(30), DATENAME(weekday, dateadd(day, -1 * day(dateadd(month, 1, @Date)), dateadd(month, 1, @Date))), 111);
        end;

    if @DateFormat = 'YYYY-MM-DD'
        begin
            declare @DAY char(2),
                    @MONTH char(2);

            select @DAY = DAY(@Date);
            if LEN(@DAY) < 2
                begin
                    select @DAY = '0'+@DAY
                end;

            select @MONTH = MONTH(@Date);
            if LEN(@MONTH) < 2
                begin
                    select @MONTH = '0'+@MONTH
                end;
            set @myRes = CONVERT(varchar(4), Year(@Date))+'-'+@MONTH+'-'+@DAY;
        end;

    -- Return Results --
    return @myRes;
end;