Re: [libreoffice-users] Calc formula for US Thanksgiving date

2012/12/3 Dennis E. Hamilton <dennis.hamilton@acm.org>:
> You should get a lot of responses on this.


Actually, I responded quite a few times, but unfortunately I forgot
(as usual) about the ”new” nad odd behaviour of this list, so I only
responded directly to the OP. That was not my intention, though, so
here is a short summary, just in case someone happens to be
interested:

A1: Year
B1: =IF(WEEKDAY(DATE(A1;10;31);2)<4;4;11)-WEEKDAY(DATE(A1;10;31);2)+21

The WEEKDAY thing is always calculated twice, which could feel a bit
unnecessary. Could be avoided by using a cell for subtotal:

A1: Year
B1: WEEKDAY(DATE(A1;10;31);2)
C1: =IF(B1<4;4;11)-B1+21

Here's a macro that does the whole thing:
REM ***** BASIC *****

Function Thanksgiving(Year As Long) As Date
Dim DayOfWeek As Long

DayOfWeek=WeekDay(DateSerial(Year,10,31))
If DayOfWeek<5 Then
Thanksgiving=DateSerial(Year,11,26-DayOfWeek)
Else
Thanksgiving=DateSerial(Year,11,33-DayOfWeek)
EndIf
End Function

REM ***** END OF BASIC *****
A1: Year
B1: =THANKSGIVING(A1)





> US Thanksgiving is always the 4th Thursday in November.
>
> So, the first thing you want to do is find out what day of the week November 1, yyyy, in a 
> particular year is. (There are functions for this).

I found the whole thing a bit easier if I started by finding out the
weekday of 31 October, but I guess it's just another way of doing it.


> Then find out how many days later the first Thursday is.  (In 2012, the answer is 0.)  You'll 
> have to work this out based on how day-of-week is counted.
>
> Add that number of days and 21 more to the November 1, yyyy date value.  That will show you the 
> date of Thanksgiving in year yyyy.  (For 2012, the correct answer is November 22, 2012.)
>
>  - Dennis
>
> -----Original Message-----
> From: . [mailto:Look@eBookRing.net]
> Sent: Monday, December 03, 2012 02:59
> To: users@global.libreoffice.org
> Subject: [libreoffice-users] Calc formula for US Thanksgiving date
>
> I need a formula for Calc to determine the US Thanksgiving date for a
> given year.
>
> Thanks
>
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