diff --git a/chrome/content/zotero/xpcom/utilities.js b/chrome/content/zotero/xpcom/utilities.js
index d80445f34..22cd66710 100644
--- a/chrome/content/zotero/xpcom/utilities.js
+++ b/chrome/content/zotero/xpcom/utilities.js
@@ -1657,6 +1657,7 @@ Zotero.Utilities = {
 					// add year, month, and day, if they exist
 					dateParts.push(dateObj.year);
 					if(dateObj.month !== undefined) {
+						// strToDate() returns a JS-style 0-indexed month, so we add 1 to it
 						dateParts.push(dateObj.month+1);
 						if(dateObj.day) {
 							dateParts.push(dateObj.day);