These time periods are displayed by the core function format_time() defined in moodlelib.php. The order numeral-space-noun is hardcoded there. The nouns use the strings like "day", "days", "hour", "hours" etc all defined in the "core" component (moodle.php).
If there is no acceptable way in your language how to compose this with the given order, please fill a bug report with a reference to this thread. Thanks.