The node.tpl.php template contains untranslatable texts 'Posted on"and "By". you will only notice so, if the option to display submission info has been enabled for a content type. to solve, either:

  • use the standard text and use translation and the string overrides module to change it to your likings
  • define your own translatable string in tempalte.php
  • use a format that should not have to be translated.

For an example of the latter see garland/template.php:

/**
 * Override or insert variables into the node template.
 */
function garland_preprocess_node(&$vars) {
  $vars['submitted'] = $vars['date'] . ' — ' . $vars['name'];
}

/**
 * Override or insert variables into the comment template.
 */
function garland_preprocess_comment(&$vars) {
  $vars['submitted'] = $vars['created'] . ' — ' . $vars['author'];
}