Rename a bunch of files with embedded dates as ISO 8601 dates.

rename_files_iso8601.ps1

#
# rename a bunch of files as follows
#
#     DDMONYYYY_NAME.EXT ==> YYYY-MM-DD_NAME.EXT
#
# i.e. it changes the date to ISO 8601 form
#


# for each file in the local path
Get-ChildItem -name |% {

  # old filename is in the form DDMONYYYY_NAME.EXT (e.g. 26APR1982_foobar.txt)
  $old_filename = $_;

  # extract the date part (e.g., 26APR1982)
  $old_date_string = $($old_filename.Substring(0, 9));

  # extract the suffix part (e.g.. foobar.txt);
  $filename_suffix = $_.Substring(10);

  # convert the date part to a date object
  $date = [datetime]::Parse($old_date_string);

  # represent the date object as a ISO 8601 date (e.g., 1982-04-26)
  $new_date_string = $date.ToString("yyyy-MM-dd");

  # build up the new filename (e.g. 1982-04-26_foobar.txt)
  $new_filename = [string]::join("_", ($new_date_string, $filename_suffix));

  # rename the file
  move $old_filename $new_filename;
}