function Get-SPOWebs(){

param(

   $Url = $(throw "Please provide a Site Collection Url"),

   $Credential = $(throw "Please provide a Credentials")

)

  $context = New-Object Microsoft.SharePoint.Client.ClientContext($Url)  

  $context.Credentials = $Credential 

  $web = $context.Web

  $context.Load($web)

  $context.Load($web.Webs)

  $context.ExecuteQuery()

  foreach($web in $web.Webs)

  {

       Get-SPOWebs -Url $web.Url -Credential $Credential 

       $web

  }

}

 Add-PSSnapin Microsoft.SharePoint.PowerShell -ErrorAction SilentlyContinue

[System.Reflection.Assembly]::LoadWithPartialName(“Microsoft.Office.Server.Search.Query”)  

[String]$lastDate = "1/1/2018"

foreach($sc in $webapplication | Get-SPSite -Limit All)

{

    Write-Host $sc.Url -ForegroundColor Yellow

    $keywordQuery = New-Object Microsoft.Office.Server.Search.Query.KeywordQuery($sc)

    $keywordQuery.QueryText = "ContentClass:STS_ListItem AND LastModifiedTime>=$($lastDate) AND site:$($sc.Url)"

    $keywordQuery.RowLimit = 5;

    $searchExec = New-Object Microsoft.Office.Server.Search.Query.SearchExecutor

    $searchResults = $searchExec.ExecuteQuery($keywordQuery)

    If( 0 -eq $searchResults.Table.Count ){

        Write-Host "`tSite Collection $($sc.Url) is old" -ForegroundColor Red

}