DateTime objects are amazing.  You can format them in so many different ways, but they also come with a boatload formats pre-defined.  Oh, and it uses the current culture.  So much cleaner.  But which is which?

$i = 0; (Get-Date).GetDateTimeFormats() | Select-Object @{name = 'index'; expression = {$i; $null = $global:i++ }}, @{name = 'output'; expression = {$_;}}

This also uses one of my favourite tricks recently - synthetic properties from Select-Object, instead of using the rigamarole that is New-Object and then Add-Member.

Anyhow, here is the output (for my culture, that is - your mileage may vary):

index output

----- ------

    0 5/15/2010

    1 5/15/10

    2 05/15/10

    3 05/15/2010

    4 10/05/15

    5 2010-05-15

    6 15-May-10

    7 Saturday, May 15, 2010

    8 May 15, 2010

    9 Saturday, 15 May, 2010

   10 15 May, 2010

   11 Saturday, May 15, 2010 9:09 AM

   12 Saturday, May 15, 2010 09:09 AM

   13 Saturday, May 15, 2010 9:09

   14 Saturday, May 15, 2010 09:09

   15 May 15, 2010 9:09 AM

   16 May 15, 2010 09:09 AM

   17 May 15, 2010 9:09

   18 May 15, 2010 09:09

   19 Saturday, 15 May, 2010 9:09 AM

   20 Saturday, 15 May, 2010 09:09 AM

   21 Saturday, 15 May, 2010 9:09

   22 Saturday, 15 May, 2010 09:09

   23 15 May, 2010 9:09 AM

   24 15 May, 2010 09:09 AM

   25 15 May, 2010 9:09

   26 15 May, 2010 09:09

   27 Saturday, May 15, 2010 9:09:59 AM

   28 Saturday, May 15, 2010 09:09:59 AM

   29 Saturday, May 15, 2010 9:09:59

   30 Saturday, May 15, 2010 09:09:59

   31 May 15, 2010 9:09:59 AM

   32 May 15, 2010 09:09:59 AM

   33 May 15, 2010 9:09:59

   34 May 15, 2010 09:09:59

   35 Saturday, 15 May, 2010 9:09:59 AM

   36 Saturday, 15 May, 2010 09:09:59 AM

   37 Saturday, 15 May, 2010 9:09:59

   38 Saturday, 15 May, 2010 09:09:59

   39 15 May, 2010 9:09:59 AM

   40 15 May, 2010 09:09:59 AM

   41 15 May, 2010 9:09:59

   42 15 May, 2010 09:09:59

   43 5/15/2010 9:09 AM

   44 5/15/2010 09:09 AM

   45 5/15/2010 9:09

   46 5/15/2010 09:09

   47 5/15/10 9:09 AM

   48 5/15/10 09:09 AM

   49 5/15/10 9:09

   50 5/15/10 09:09

   51 05/15/10 9:09 AM

   52 05/15/10 09:09 AM

   53 05/15/10 9:09

   54 05/15/10 09:09

   55 05/15/2010 9:09 AM

   56 05/15/2010 09:09 AM

   57 05/15/2010 9:09

   58 05/15/2010 09:09

   59 10/05/15 9:09 AM

   60 10/05/15 09:09 AM

   61 10/05/15 9:09

   62 10/05/15 09:09

   63 2010-05-15 9:09 AM

   64 2010-05-15 09:09 AM

   65 2010-05-15 9:09

   66 2010-05-15 09:09

   67 15-May-10 9:09 AM

   68 15-May-10 09:09 AM

   69 15-May-10 9:09

   70 15-May-10 09:09

   71 5/15/2010 9:09:59 AM

   72 5/15/2010 09:09:59 AM

   73 5/15/2010 9:09:59

   74 5/15/2010 09:09:59

   75 5/15/10 9:09:59 AM

   76 5/15/10 09:09:59 AM

   77 5/15/10 9:09:59

   78 5/15/10 09:09:59

   79 05/15/10 9:09:59 AM

   80 05/15/10 09:09:59 AM

   81 05/15/10 9:09:59

   82 05/15/10 09:09:59

   83 05/15/2010 9:09:59 AM

   84 05/15/2010 09:09:59 AM

   85 05/15/2010 9:09:59

   86 05/15/2010 09:09:59

   87 10/05/15 9:09:59 AM

   88 10/05/15 09:09:59 AM

   89 10/05/15 9:09:59

   90 10/05/15 09:09:59

   91 2010-05-15 9:09:59 AM

   92 2010-05-15 09:09:59 AM

   93 2010-05-15 9:09:59

   94 2010-05-15 09:09:59

   95 15-May-10 9:09:59 AM

   96 15-May-10 09:09:59 AM

   97 15-May-10 9:09:59

   98 15-May-10 09:09:59

   99 May 15

  100 May 15

  101 2010-05-15T09:09:59.0464946-07:00

  102 2010-05-15T09:09:59.0464946-07:00

  103 Sat, 15 May 2010 09:09:59 GMT

  104 Sat, 15 May 2010 09:09:59 GMT

  105 2010-05-15T09:09:59

  106 9:09 AM

  107 09:09 AM

  108 9:09

  109 09:09

  110 9:09:59 AM

  111 09:09:59 AM

  112 9:09:59

  113 09:09:59

  114 2010-05-15 09:09:59Z

  115 Saturday, May 15, 2010 4:09:59 PM

  116 Saturday, May 15, 2010 04:09:59 PM

  117 Saturday, May 15, 2010 16:09:59

  118 Saturday, May 15, 2010 16:09:59

  119 May 15, 2010 4:09:59 PM

  120 May 15, 2010 04:09:59 PM

  121 May 15, 2010 16:09:59

  122 May 15, 2010 16:09:59

  123 Saturday, 15 May, 2010 4:09:59 PM

  124 Saturday, 15 May, 2010 04:09:59 PM

  125 Saturday, 15 May, 2010 16:09:59

  126 Saturday, 15 May, 2010 16:09:59

  127 15 May, 2010 4:09:59 PM

  128 15 May, 2010 04:09:59 PM

  129 15 May, 2010 16:09:59

  130 15 May, 2010 16:09:59

  131 May, 2010

  132 May, 2010