The Moodle doesn't show the correct date in Russian if i write follows:
<?php echo userdate(time(), get_string('strftimedaydate', 'core_langconfig')); ?>
As a result of the following line will be displayed:
вторник 19 Август 2014
Usually, the date is displayed as follows:
Вторник, 19 Августа 2014

In order to put a comma ater the day of the week need to make the following corrections:
en langconfig.php:
$string ['strftimedaydate'] = '%A, %d %B %Y'
$string ['strftimedayshort'] = '%A, %d %B'
ru langconfig.php:
$string['strftimedaydate'] = '%A %d %B %Y'; // <== '%A, %d %B %Y'
$string['strftimedayshort'] = '%A %d %B'; // <== '%A, %d %B'

In Russian the months alter form to reflect the case, i.e. see file editor_tinymce.php:
$string['insertdatetime:months_long'] = '...'
This is the correct substitution!