Index: regenerate-thumbnails.php
===================================================================
--- regenerate-thumbnails.php	(revision 49478)
+++ regenerate-thumbnails.php	(revision 49749)
@@ -164,7 +164,18 @@
 				// Directly querying the database is normally frowned upon, but all
 				// of the API functions will return the full post objects which will
 				// suck up lots of memory. This is best, just not as future proof.
-				if ( ! $images = $wpdb->get_results( "SELECT ID FROM $wpdb->posts WHERE post_type = 'attachment' AND post_mime_type LIKE 'image/%' ORDER BY ID DESC" ) ) {
+
+				// If a month was selected, let's validate it and plug it into query.
+				// The month date should be in format YYYY/MM
+				if ( ! empty( $_POST['regenerate-thumbnails-date'] ) ) {
+					if ( preg_match( '/(\d{4})\/(\d{2})/', $_POST['regenerate-thumbnails-date'], $date_parts ) ) {
+						$month = $date_parts[1] . '/' . $date_parts[2];
+					}
+				}
+				// Next, build the SQL to inject into query
+				$where_date = !empty( $month ) ? "AND DATE_FORMAT(post_date, '%Y/%m') = '$month'" : "";
+
+				if ( ! $images = $wpdb->get_results( "SELECT ID FROM $wpdb->posts WHERE post_type = 'attachment' AND post_mime_type LIKE 'image/%' $where_date ORDER BY ID DESC" ) ) {
 					echo '	<p>' . sprintf( __( "Unable to find any images. Are you sure <a href='%s'>some exist</a>?", 'regenerate-thumbnails' ), admin_url( 'upload.php?post_mime_type=image' ) ) . "</p></div>";
 					return;
 				}
@@ -327,6 +338,10 @@
 
 	<p><?php _e( 'To begin, just press the button below.', 'regenerate-thumbnails '); ?></p>
 
+	<p>
+		<?php _e( 'Month to regenerate, in format YYYY/MM (leave blank to include all images)', 'regenerate-thumbnails' ); ?>
+		<input type="textfield" class="hide-if-no-js" name="regenerate-thumbnails-date" id="regenerate-thumbnails-date" value="<?php print date('Y/m'); ?>" />
+	</p>
 	<p><input type="submit" class="button hide-if-no-js" name="regenerate-thumbnails" id="regenerate-thumbnails" value="<?php _e( 'Regenerate All Thumbnails', 'regenerate-thumbnails' ) ?>" /></p>
 
 	<noscript><p><em><?php _e( 'You must enable Javascript in order to proceed!', 'regenerate-thumbnails' ) ?></em></p></noscript>
@@ -396,4 +411,4 @@
 	$RegenerateThumbnails = new RegenerateThumbnails();
 }
 
-?>
\ No newline at end of file
+?>