Calendar Table - Week number of month

Question

I have a calendar table with data from year 2000 to 2012 (2012 wasn't intentional!). I just realize that I don't have the week number of month (e.g In January 1,2,3,4 February 1,2,3,4)

How do I go about calculating the week numbers in a month to fill this table?

Here is the table schema

CREATE TABLE [TCalendar] (
    [TimeKey] [int] NOT NULL ,
    [FullDateAlternateKey] [datetime] NOT NULL ,
    [HolidayKey] [tinyint] NULL ,
    [IsWeekDay] [tinyint] NULL ,
    [DayNumberOfWeek] [tinyint] NULL ,
    [EnglishDayNameOfWeek] [nvarchar] (10) COLLATE SQL_Latin1_General_CP1_CI_AS NULL ,
    [SpanishDayNameOfWeek] [nvarchar] (10) COLLATE SQL_Latin1_General_CP1_CI_AS NULL ,
    [FrenchDayNameOfWeek] [nvarchar] (10) COLLATE SQL_Latin1_General_CP1_CI_AS NULL ,
    [DayNumberOfMonth] [tinyint] NULL ,
    [DayNumberOfYear] [smallint] NULL ,
    [WeekNumberOfYear] [tinyint] NULL ,
    [EnglishMonthName] [nvarchar] (10) COLLATE SQL_Latin1_General_CP1_CI_AS NULL ,
    [SpanishMonthName] [nvarchar] (10) COLLATE SQL_Latin1_General_CP1_CI_AS NULL ,
    [FrenchMonthName] [nvarchar] (10) COLLATE SQL_Latin1_General_CP1_CI_AS NULL ,
    [MonthNumberOfYear] [tinyint] NULL ,
    [CalendarQuarter] [tinyint] NULL ,
    [CalendarYear] [char] (4) COLLATE SQL_Latin1_General_CP1_CI_AS NULL ,
    [CalendarSemester] [tinyint] NULL ,
    [FiscalQuarter] [tinyint] NULL ,
    [FiscalYear] [char] (4) COLLATE SQL_Latin1_General_CP1_CI_AS NULL ,
    [FiscalSemester] [tinyint] NULL ,
    [IsLastDayInMonth] [tinyint] NULL ,
    CONSTRAINT [PK_TCalendar] PRIMARY KEY  CLUSTERED 
    (
        [TimeKey]
    )  ON [PRIMARY] 
) ON [PRIMARY]
GO

Answer 1

update TCalendar 
set = WeekNumberOfMonth = DATEDIFF(week, DATEADD(MONTH, DATEDIFF(MONTH, 0, FullDateAlternateKey), 0), FullDateAlternateKey) +1