$source = "R:\"

Get-ChildItem -LiteralPath $source -File | ForEach-Object {

$year = $_.LastWriteTime.Year.ToString()

$dest = Join-Path $source $year

if (-not (Test-Path -LiteralPath $dest)) { New-Item -Path $dest -ItemType Directory | Out-Null }

Move-Item -LiteralPath $_.FullName -Destination $dest

}