new Intl.DateTimeFormat('ru-RU', { weekday: 'short' }).format(new Date()) //пн

const collator = new Intl.Collator(undefined, { numeric: true, sensitivity: 'base' });
array.sort(collator.compare);

pkg install pecl-intl

<?php
$formatter = new IntlDateFormatter('ru_RU', IntlDateFormatter::FULL, IntlDateFormatter::FULL);
$formatter->setPattern('d MMMM YYYY, HH:mm');
echo $formatter->format(new DateTime('2015-01-01 01:01:01')); //1 января 2015, 01:01