The language that needs to be in use.
Examples
German
<input id="input" width="276" />
<script>
$('#input').datetimepicker({
locale: 'de-de',
format: 'HH:MM dd mmm yyyy'
});
</script>
Bulgarian
<input id="input" width="276" />
<script>
$('#input').datetimepicker({
locale: 'bg-bg',
format: 'HH:MM dd mmm yyyy',
datepicker: { weekStartDay: 1 }
});
</script>