How do I parse a date in PowerShell?

Question

I write a script that removes backups older than five days. I check it by the name of the directory and not the actual date.

How do parse the directory name to a date to compare them?

Part of my script:

...

foreach ($myDir in $myDirs)
{
  $dirName=[datetime]::Parse($myDir.Name)
  $dirName= '{0:dd-MM-yyyy}' -f $dirName
  if ($dirName -le "$myDate")
  {
        remove-item $myPath\$dirName -recurse
  }
}
...

Maybe I do something wrong, because it still does not remove last month's directories.

The whole script with Akim's suggestions is below:

Function RemoveOldBackup([string]$myPath)
{

  $myDirs = Get-ChildItem $myPath

  if (Test-Path $myPath)
  {
    foreach ($myDir in $myDirs)
    {
      #variable for directory date
      [datetime]$dirDate = New-Object DateTime

      #check that directory name could be parsed to DateTime
      if([datetime]::TryParse($myDir.Name, [ref]$dirDate))
      {
            #check that directory is 5 or more day old
            if (([DateTime]::Today - $dirDate).TotalDays -ge 5)
            {
                  remove-item $myPath\$myDir -recurse
            }
      }
    }
  }
  Else
  {
    Write-Host "Directory $myPath does not exist!"
  }
}

RemoveOldBackup("E:\test")

Directories names are, for example, 09-07-2012, 08-07-2012, ..., 30-06-2012, and 29-06-2012.

Could you try folowing steps in powershell console: 1. [DateTime] $a = New-Object DateTime; [DateTime]::TryParse("29-06-2012", [ref]$a); $a; ([DateTime]::Today - $a) -ge 5; 2. [DateTime]::TryParseExact("29-06-2012", "dd-MM-yyyy", [System.Globalization.CultureInfo]::InvariantCulture, [System.Globalization.DateTimeStyles]::None, [ref]$a); $a; 3. [DateTime]::TryParseExact("29-06-2012", "dd-MM-yyyy", [System.Globalization.CultureInfo]::InvariantCulture, [System.Globalization.DateTimeStyles]::None, [ref]$a); ([DateTime]::Today - $a) -ge 5. All sould be without errors. — Akim
– Akim, Commented Jul 9, 2012 at 13:18
results in polish: 1) False 1 stycznia 0001 00:00:00 True, 2) True 29 czerwca 2012 00:00:00, 3) True True — Mirek
– Mirek, Commented Jul 9, 2012 at 13:32
Ok @Mirek, you have a culture at your sever that does not understand your dates correctly. it simple thinks that "01-02-2012" is 1st of February, but not 2nd of January. I'm going to update snippet in my answer — Akim
– Akim, Commented Jul 9, 2012 at 13:37
As a side note, if you ever want to sort your directories/files by name, use yyyy-MM-dd naming scheme. — MKesper
– MKesper, Commented Mar 4, 2016 at 8:11

Ryan · Accepted Answer · 2019-04-25 01:17:56Z

26

Try to calculate the difference between [DateTime]::Today and the result of parsing the directory name:

foreach ($myDir in $myDirs)
{
    # Variable for directory date
    [datetime]$dirDate = New-Object DateTime

    # Check that directory name could be parsed to DateTime
    if ([DateTime]::TryParseExact($myDir.Name, "dd-MM-yyyy",
                                  [System.Globalization.CultureInfo]::InvariantCulture,
                                  [System.Globalization.DateTimeStyles]::None,
                                  [ref]$dirDate))
    {
        # Check that directory is 5 or more day old
        if (([DateTime]::Today - $dirDate).TotalDays -ge 5)
        {
            remove-item $myPath\$dirName -recurse
        }
    }
}

edited Apr 25, 2019 at 1:17

Ryan

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answered Jul 9, 2012 at 10:53

Akim

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4 Comments

Mirek Over a year ago

more or less it works for me but less means it doesn't remove last month dirs

Akim Over a year ago

Try to replace .Days with .TotalDays. See updated snippet

Akim Over a year ago

Now this snippet is culture invariant, could you try it?

Anderson Pimentel Over a year ago

A little late, but I think [DateTime]::Today - $dirName should be [DateTime]::Today - $dirDate.

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