Last Weekday of Month

# Get last day of Month
$LastWeekDay = (Get-Date $date.Date -day 1).AddMonths(1).AddMilliseconds(-1)
# if day is Sat or Sun subtract days until it is not
while(0,6 -contains $LastWeekDay.DayOfWeek.value__){
    $LastWeekDay = $LastWeekDay.AddDays(-1)
}
$LastWeekDay

Details

Returns the last weekday of the month for any given date.

Example

PS C:\> $date = Get-Date '6/1/2019'
>> $LastWeekDay = (Get-Date $date.Date -day 1).AddMonths(1).AddMilliseconds(-1)
>> while(0,6 -contains $LastWeekDay.DayOfWeek.value__){
>>     $LastWeekDay = $LastWeekDay.AddDays(-1)
>> }
>> $LastWeekDay


Friday, June 28, 2019 11:59:59 PM