--- a/toolkit/content/widgets/datepicker.js
+++ b/toolkit/content/widgets/datepicker.js
@@ -280,18 +280,21 @@ function DatePicker(context) {
    *          {Function} setMonth
    *          {Function} getMonthString
    *          {Array<String>} datetimeOrders
    *        }
    * @param {DOMElement} context
    */
   function MonthYear(options, context) {
     const spinnerSize = 5;
-    const yearFormat = new Intl.DateTimeFormat(options.locale, { year: "numeric" }).format;
-    const dateFormat = new Intl.DateTimeFormat(options.locale, { year: "numeric", month: "long" }).format;
+    const yearFormat = new Intl.DateTimeFormat(options.locale, { year: "numeric",
+                                                                 timeZone: "UTC" }).format;
+    const dateFormat = new Intl.DateTimeFormat(options.locale, { year: "numeric",
+                                                                 month: "long",
+                                                                 timeZone: "UTC" }).format;
     const spinnerOrder =
       options.datetimeOrders.indexOf("month") < options.datetimeOrders.indexOf("year") ?
       "order-month-year" : "order-year-month";
 
     context.monthYearView.classList.add(spinnerOrder);
 
     this.context = context;
     this.state = { dateFormat };
@@ -307,17 +310,17 @@ function DatePicker(context) {
         viewportSize: spinnerSize
       }, context.monthYearView),
       year: new Spinner({
         id: "spinner-year",
         setValue: year => {
           this.state.isYearSet = true;
           options.setYear(year);
         },
-        getDisplayString: year => yearFormat(new Date(new Date(0).setFullYear(year))),
+        getDisplayString: year => yearFormat(new Date(new Date(0).setUTCFullYear(year))),
         viewportSize: spinnerSize
       }, context.monthYearView)
     };
 
     this._attachEventListeners();
   }
 
   MonthYear.prototype = {