diff --git a/lib/dateHelper.js b/lib/dateHelper.js
index f4fcf2d..e62ccd9 100644
--- a/lib/dateHelper.js
+++ b/lib/dateHelper.js
@@ -2,7 +2,7 @@ import moment from 'moment'
 
 export function getDays({ startDate, endDate }) {
   let currentDay = moment(startDate)
-  const days = [currentDay.format('YYYY-MM-DD')]
+  const days = [dateFormat(currentDay)]
 
   if (!endDate) {
     return days
@@ -11,8 +11,15 @@ export function getDays({ startDate, endDate }) {
   const end = moment(endDate)
   while (currentDay < end) {
     currentDay = currentDay.add(1, 'day')
-    days.push(currentDay.format('YYYY-MM-DD'))
+    days.push(dateFormat(currentDay))
   }
 
   return days
 }
+
+export function dateFormat(date) {
+  if (!date) {
+    return null
+  }
+  return moment(date).format('YYYY-MM-DD')
+}