If you’d like to find out how long it is until next Sunday (or how many days have passed since last Sunday), simply use the property DayOfWeek. It is a number telling you the current day of the week. So it’s easy to calculate the difference between the current DayOfWeek and the index number of Sunday:
[Int]$index = Get-Date | Select-Object -ExpandProperty DayOfWeek $daysTillNextSunday = 7 - $index $daysSinceLastSunday = $index $NextSunday = (Get-Date) + (New-TimeSpan -Days $daysTillNextSunday) $LastSunday = (Get-Date) - (New-TimeSpan -Days $daysSinceLastSunday) $NextSunday $LastSunday