$date.Date.AddDays(6-($date).DayOfWeek.value__)
PS C:\> $Date = Get-Date >> $date.Date.AddDays(6-($date).DayOfWeek.value__) Saturday, March 30, 2019 12:00:00 AM
$date.Date.AddDays(6-($date).DayOfWeek.value__)
ExamplePS C:\> $Date = Get-Date >> $date.Date.AddDays(6-($date).DayOfWeek.value__) Saturday, March 30, 2019 12:00:00 AM