NthDayOfMonth ( N ; shortDayName ; monthNo ; yearNo )

Provides the Nth occurrence of an abbreviated "day name" for a given month and year

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Ralph Learmont - Show more from this author

Sample input:

To get the 4th Sunday for October 2023 enter: NthDayOfMonth ( 4 ; "Sun" ; 10 ; 2023 )

Sample output:

22/10/2023 //Depends on country's date format. Here it's 22nd October 2023

Function definition: (Copy & paste into FileMaker's Edit Custom Function window)

Syntax:  NthDayOfMonth ( N ; shortDayName ; monthNo ; yearNo )



Let ( [

DateFirst = Date ( monthNo ; 1 ; yearNo ) ;
NameFirst = Left ( DayName ( DateFirst ) ; 3 ) ;

String = "MonTueWedThuFriSatSunMonTueWedThuFriSatSun" ;
Start = Position ( String ; NameFirst ; 1 ; 1 ) ;
Finish = Position ( String ; shortDayName ; Start ; 1 ) ;
DaysBetween = (Finish - Start)/3 ;
dayNo = DaysBetween + 1 + 7*(N-1) ] ;


Date ( monthNo ; dayNo ; yearNo ))




/*  Devised by Ralph Learmont 25th Apr 2023

Example:
To get the 4th Sunday for October 2023 enter
NthDayOfMonth ( 4 ; "Sun" ; 10 ; 2023 )

*/

Important: Use the short 3 character dayName such as "Sun" , "Mon" , "Tue" etc.

Instead of using a day's number such as seen in Filemaker's "DayOfWeek" function, I found it's easier to refer directly to a day's literal name rather than having to remember for example if a "Sunday" is the 1st or the 7th day of a week.

I found it useful for providing an ongoing calendar of monthly events (based on a pattern), such as the monthly "Market Day" to be held "on the 4th Sunday" of every month.

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NthDayOfMonth ( N ; shortDayName ; monthNo ; yearNo )

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