The time of day in RecentChanges and Watchlist will be rendered in ContentLang independant of the language set in the preferences. There's no reason to do so, as the dates in the same list are rendered in the user's language.
The relevant line of code seems to be line 550 in ChangesList.php, which is:
$time = $wgContLang->time( $rc_timestamp, true, true );
but which should be:
$time = $wgLang->time( $rc_timestamp, true, true );