>I have a cross tab of production by week based on daily production reports. I originaly had the first column to be weeks indentified as 1,2,3 etc. The client wants the first column to be "Week Beginning Date". Is there a simple way to convert the week to display the first day of that week?
>
>Thanks
>Gaylen

Gaylen,

Having assigned week numbers means that you have defined what the first day of the first week of that year is (see help about week())

date(first day of week(n)) = date(first day of week(1)) + 7 * ( n - 1)

I am including some iso things about dates which you may find useful (don't remember from where I picked it up)

The ISO 8601 rule is: The first week of the year is the week containing the first Thursday
 
 
Algorithm Conventions:
   "/" = integer division, discard remainder  (5/2 = 2)
   "%" = modulus, keep only remainder    (5%2 = 1)
   "&" = concatenation   ("W" & 12 = "W12")
   "!=" = unequal   (7 != 8  is true)
   "+=" = add right value to left variable,
             if F = 3, then (F += 4) yields F = 7
   "-=" = subtract right value from left variable

1. Convert input to Y M D
   Y = Year     (full specification; input 98 = year 0098)
   M = Month    (1 through 12)
   D = Day      (1 through 31)
2. Find if Y is LeapYear
   if (Y % 4 = 0  and  Y % 100 != 0) or Y % 400 = 0
      then
         Y is LeapYear
      else
         Y is not LeapYear
3. Find if Y-1 is LeapYear
4. Find the DayOfYearNumber for Y M D
   Mnth[1] = 0    Mnth[4] = 90    Mnth[7] = 181   Mnth[10] = 273
   Mnth[2] = 31   Mnth[5] = 120   Mnth[8] = 212   Mnth[11] = 304
   Mnth[3] = 59   Mnth[6] = 151   Mnth[9] = 243   Mnth[12] = 334
   DayOfYearNumber = D + Mnth[M]
   if Y is LeapYear and M > 2
      then
         DayOfYearNumber += 1
5. Find the Jan1Weekday for Y (Monday=1, Sunday=7)
   YY = (Y-1) % 100
   C = (Y-1) - YY
   G = YY + YY/4
   Jan1Weekday = 1 + (((((C / 100) % 4) x 5) + G) % 7)
6. Find the Weekday for Y M D
   H = DayOfYearNumber + (Jan1Weekday - 1)
   Weekday = 1 + ((H -1) % 7)
7. Find if Y M D falls in YearNumber Y-1, WeekNumber 52 or 53
   if DayOfYearNumber <= (8-Jan1Weekday) and Jan1Weekday > 4
      then
         YearNumber = Y - 1 
         if Jan1Weekday = 5 or (Jan1Weekday = 6 and Y-1 is LeapYear)
            then
               WeekNumber = 53
            else 
               WeekNumber = 52
      else 
         YearNumber = Y
8. Find if Y M D falls in YearNumber Y+1, WeekNumber 1
   if YearNumber = Y
      then
         if Y is LeapYear
            then 
               I = 366
               else
               I = 365
         if (I - DayOfYearNumber) < (4 - Weekday)
            then
               YearNumber = Y + 1
               WeekNumber = 1
9. Find if Y M D falls in YearNumber Y, WeekNumber 1 through 53
   if YearNumber = Y
      then
         J = DayOfYearNumber + (7 - Weekday) + (Jan1Weekday -1)
         WeekNumber = J / 7
         if Jan1Weekday > 4
               WeekNumber -= 1
10. Output ISO Week Date:
   if WeekNumber < 10
      then
         WeekNumber = "0" & WeekNumber  (WeekNumber requires 2 digits)
   YearNumber - WeekNumber - Weekday    (Optional: "W" & WeekNumber)