diff --git a/chrome/content/zotero/xpcom/date.js b/chrome/content/zotero/xpcom/date.js
index c41b5eec5..d34c326a3 100644
--- a/chrome/content/zotero/xpcom/date.js
+++ b/chrome/content/zotero/xpcom/date.js
@@ -330,6 +330,8 @@ Zotero.Date = new function(){
 				}
 				
 				if(date.month) date.month--;		// subtract one for JS style
+				else delete date.month;
+				
 				Zotero.debug("DATE: retrieved with algorithms: "+JSON.stringify(date));
 				
 				parts.push(
@@ -369,7 +371,7 @@ Zotero.Date = new function(){
 		}
 		
 		// MONTH
-		if(!date.month) {
+		if(date.month === undefined) {
 			// compile month regular expression
 			var months = ['jan', 'feb', 'mar', 'apr', 'may', 'jun', 'jul',
 				'aug', 'sep', 'oct', 'nov', 'dec'];
diff --git a/chrome/content/zotero/xpcom/utilities.js b/chrome/content/zotero/xpcom/utilities.js
index ef161a193..e24ece3a4 100644
--- a/chrome/content/zotero/xpcom/utilities.js
+++ b/chrome/content/zotero/xpcom/utilities.js
@@ -1611,7 +1611,7 @@ Zotero.Utilities = {
 					cslItem[variable] = {"date-parts":[dateParts]};
 					
 					// if no month, use season as month
-					if(dateObj.part && !dateObj.month) {
+					if(dateObj.part && dateObj.month === undefined) {
 						cslItem[variable].season = dateObj.part;
 					}
 				} else {
diff --git a/test/tests/data/citeProcJSExport.js b/test/tests/data/citeProcJSExport.js
index 3678e9909..67cb3f87f 100644
--- a/test/tests/data/citeProcJSExport.js
+++ b/test/tests/data/citeProcJSExport.js
@@ -1347,8 +1347,7 @@
 					1,
 					2
 				]
-			],
-			"season": "2000-01-02"
+			]
 		},
 		"title": "Title",
 		"type": "patent"