Add translation to days of the week

Not sure if this is a bug or even if there is a better way to do it. During the content creation form I wanted to translate the days of the weeks. I could managed it modifying the line 69 in the office_hours.elements file:

  if (!($element['#weight'] & 1)) { //first cell
    $element['#prefix'] = '<div class="office-hours-block"><div class="dayname">' . $days[$day] . '</div>';
  }

to:

if (!($element['#weight'] & 1)) { //first cell
    $element['#prefix'] = '<div class="office-hours-block"><div class="dayname">' . t($days[$day]) . '</div>';
  }

If you know a better solution please tell me. Thanks!