lastPairedWeekendsInRange ( startDate ; endDate )

Returns a return-separated list of FileMaker-formatted dates representing the last Weekends of each month between the start and end dates where both Saturday and Sunday fall within the same month.

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Sample input:

lastPairedWeekendsInRange ( Get ( CurrentDate ) ; Get ( CurrentDate ) + 365 )

Sample output:

28/06/2025
29/06/2025
26/07/2025
27/07/2025
30/08/2025
31/08/2025

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

// LAST PAIRED WEEKENDS IN RANGE

// Returns a return-separated list of FileMaker-formatted dates representing 
// the last Weekends of each month between the start and end dates where both
// Saturday and Sunday fall within the same month.

// Function Name : lastPairedWeekendsInRange
// Parameters : startDate ; endDate
// Use example : lastPairedWeekendsInRange ( Get ( CurrentDate ) ; Get ( CurrentDate ) + 365 )

Let ( [

    // Current month context
    y = Year ( startDate ) ;
    m = Month ( startDate ) ;
    firstOfMonth = Date ( m ; 1 ; y ) ;
    lastOfMonth = Date ( m + 1 ; 0 ; y ) ;
    lastDow = DayOfWeek ( lastOfMonth ) ;

    // Initial candidate for last Saturday
    candidateSaturday = lastOfMonth - Mod ( lastDow ; 7 ) ;

    // Recursive helper to find the last weekend pair in the same month
    lastWeekendPair = 
        Let ( [
            saturday = candidateSaturday ;
            sunday = saturday + 1
        ];
            If (
                Month ( sunday ) = m ;
                saturday & ¶ & sunday ; // return the valid pair
                // Step back 1 week and recurse
                Let ( [
                    newLastOfMonth = candidateSaturday - 7 ;
                    newLastDow = DayOfWeek ( newLastOfMonth ) ;
                    newCandidateSaturday = newLastOfMonth - Mod ( newLastDow ; 7 ) ;

                    // Recursive helper repeated
                    newSunday = newCandidateSaturday + 1
                ];
                    If (
                        Month ( newSunday ) = m ;
                        newCandidateSaturday & ¶ & newSunday ;
                        Let ( [
                            earlierLastOfMonth = newCandidateSaturday - 7 ;
                            earlierLastDow = DayOfWeek ( earlierLastOfMonth ) ;
                            earlierCandidateSaturday = earlierLastOfMonth - Mod ( earlierLastDow ; 7 ) ;
                            earlierSunday = earlierCandidateSaturday + 1
                        ];
                            // Deep recursion – 3 levels
                            If (
                                Month ( earlierSunday ) = m ;
                                earlierCandidateSaturday & ¶ & earlierSunday ;
                                // Add more levels if needed (FileMaker 17 max recursion: 10,000)
                                ""
                            )
                        )
                    )
                )
            )
        ) ;

    // Go to the next month
    nextMonth = Date ( m + 1 ; 1 ; y )

];
    If (
        firstOfMonth > endDate ;
        "" ;
        lastWeekendPair & ¶ & lastPairedWeekendsInRange ( nextMonth ; endDate )
    )
)

// Generates a list of dates in FileMaker Date format for the last Weekends of each 
// month within a given date range. This function uses recursion to iterate through months, 
// making it compatible with FileMaker versions prior to 18 which do not support the While function.

// GitHub : https://github.com/roxytheman/fmCustomFunctions/blob/e3b8219fc5895f379aa54ca293fc6566399450a6/functions/lastPairedWeekendsInRange.fmfn
// BD Link : https://www.briandunning.com/cf/2817
// Written by: jonni@me.com
// V 1.0

Generates a list of dates in FileMaker Date format for the last Weekends of each month within a given date range. This function uses recursion to iterate through months, making it compatible with FileMaker versions prior to 18 which do not support the While function.

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Note: these functions are not guaranteed or supported by BrianDunning.com. Please contact the individual developer with any questions or problems.

lastPairedWeekendsInRange ( startDate ; endDate )

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