diff --git a/background.js b/background.js
index 832dbf8..a1cc6d5 100644
--- a/background.js
+++ b/background.js
@@ -48,7 +48,7 @@ function bookmarkTabs() {
 	bookmarkingTabs = true;
 
 	let now = new Date();
-	let dateString = [now.getFullYear().toString(), now.getMonth().toString().padStart(2, '0'), now.getDate().toString().padStart(2, '0')].join('-');
+	let dateString = [now.getFullYear().toString(), (now.getMonth() + 1).toString().padStart(2, '0'), now.getDate().toString().padStart(2, '0')].join('-');
 	let timeString = [now.getHours().toString().padStart(2, '0'), now.getMinutes().toString().padStart(2, '0')].join(':');
 	setActionStatus('Bookmarking tabs…', 'processing', function() {
 		getOrCreateFolder(function(rootId) {