$web = Get-SPWeb -Identity https://sharepoint/sites/PowerShellTests $folder = $web.Folders["Workflows"] $property = $folder.Properties["docid_msft_hier_listid_validate"] $dt = Get-Date -Year 2100 -Month 12 -Day 31 $folder.Properties["docid_msft_hier_listid_validate"] = $dt $folder.Update() $web.Update()