<IfModule mod_rewrite.c>
....
RewriteRule ^/calendar/([0-9]+)/([0-9]+)/$ ?year=$1&month=$2
</IfModule>
array(
"CONDITION" => "#^/calendar//calendar/([0-9]+)/([0-9]+)/#",
"RULE" => "YEAR=\$1&MONTH=\$2",
"ID" => "bitrix:news.calendar",
"PATH" => "/calendar/index.php",
),