diff --git a/get-cycle-day-number.js b/get-cycle-day-number.js
index 0864b12..d7890ca 100644
--- a/get-cycle-day-number.js
+++ b/get-cycle-day-number.js
@@ -12,7 +12,13 @@ export default function config(opts) {
     // the past as we iterate over the array
     // also, to retrieve the number, we only need the cycle days before the target day
     // TODO we can probably rely on the db to do the sorting for us
-    const sorted = [...unsorted].sort((a, b) => b.date.isAfter(a.date))
+    targetDate = moment(targetDate)
+    const sorted = unsorted
+      .map(day => {
+        day.date = moment(day.date)
+        return day
+      })
+      .sort((a, b) => b.date.isAfter(a.date))
     const firstDayBeforeTargetDayIndex = sorted.findIndex(day => day.date.isBefore(targetDate))
     const cycleDays = sorted.slice(firstDayBeforeTargetDayIndex)
 
diff --git a/test/get-cycle-day.spec.js b/test/get-cycle-day.spec.js
index 87ed42d..64ee0b9 100644
--- a/test/get-cycle-day.spec.js
+++ b/test/get-cycle-day.spec.js
@@ -1,6 +1,5 @@
 import chai from 'chai'
 import dirtyChai from 'dirty-chai'
-import moment from 'moment'
 
 const expect = chai.expect
 chai.use(dirtyChai)
@@ -11,163 +10,163 @@ describe('getCycleDay', () => {
   const getCycleDayNumber = getCycleDayNumberModule()
   it('works if the last data entered is a bleeding day', function () {
     const cycleDays = [{
-      date: moment([2018, 5, 2])
+      date: new Date(2018, 5, 2)
     }, {
-      date: moment([2018, 5, 3]),
+      date: new Date(2018, 5, 3),
       bleeding: {
         value: 2
       }
     }, {
-      date: moment([2018, 5, 4])
+      date: new Date(2018, 5, 4)
     }, {
-      date: moment([2018, 5, 9]),
+      date: new Date(2018, 5, 9),
       bleeding: {
         value: 2
       }
     }, {
-      date: moment([2018, 5, 10]),
+      date: new Date(2018, 5, 10),
       bleeding: {
         value: 2
       }
     }]
-    const targetDate = moment([2018, 5, 17])
+    const targetDate = new Date(2018, 5, 17)
     const result = getCycleDayNumber(cycleDays, targetDate)
     expect(result).to.eql(9)
   })
 
   it('works if the last data entered is a non-bleeding day', function () {
     const cycleDays = [{
-      date: moment([2018, 5, 2])
+      date: new Date(2018, 5, 2)
     }, {
-      date: moment([2018, 5, 3]),
+      date: new Date(2018, 5, 3),
       bleeding: {
         value: 2
       }
     }, {
-      date: moment([2018, 5, 4])
+      date: new Date(2018, 5, 4)
     }, {
-      date: moment([2018, 5, 9]),
+      date: new Date(2018, 5, 9),
       bleeding: {
         value: 2
       }
     }, {
-      date: moment([2018, 5, 10]),
+      date: new Date(2018, 5, 10),
       bleeding: {
         value: 2
       }
     }, {
-      date: moment([2018, 5, 13])
+      date: new Date(2018, 5, 13)
     }, {
-      date: moment([2018, 5, 14])
+      date: new Date(2018, 5, 14)
     }]
 
-    const targetDate = moment([2018, 5, 17])
+    const targetDate = new Date(2018, 5, 17)
     const result = getCycleDayNumber(cycleDays, targetDate)
     expect(result).to.eql(9)
   })
 
   it('works if the cycle days are not sorted by date', function () {
     const cycleDays = [{
-      date: moment([2018, 5, 13]),
+      date: new Date(2018, 5, 13),
       bleeding: {
         value: 2
       }
     }, {
-      date: moment([2018, 5, 9]),
+      date: new Date(2018, 5, 9),
       bleeding: {
         value: 2
       }
     }, {
-      date: moment([2018, 5, 3]),
+      date: new Date(2018, 5, 3),
       bleeding: {
         value: 2
       }
     }, {
-      date: moment([2018, 5, 4])
+      date: new Date(2018, 5, 4)
     }, {
-      date: moment([2018, 5, 10]),
+      date: new Date(2018, 5, 10),
       bleeding: {
         value: 2
       }
     }, {
-      date: moment([2018, 5, 2])
+      date: new Date(2018, 5, 2)
     }]
 
-    const targetDate = moment([2018, 5, 17])
+    const targetDate = new Date(2018, 5, 17)
     const result = getCycleDayNumber(cycleDays, targetDate)
     expect(result).to.eql(5)
   })
 
   it('works when there are only bleeding days', function () {
     const cycleDays = [{
-      date: moment([2018, 5, 9]),
+      date: new Date(2018, 5, 9),
       bleeding: {
         value: 2
       }
     }, {
-      date: moment([2018, 5, 10]),
+      date: new Date(2018, 5, 10),
       bleeding: {
         value: 2
       }
     }]
-    const targetDate = moment([2018, 5, 17])
+    const targetDate = new Date(2018, 5, 17)
     const result = getCycleDayNumber(cycleDays, targetDate)
     expect(result).to.eql(9)
   })
 
   it('works if some bleedings are exluded', function () {
     const cycleDays = [{
-      date: moment([2018, 5, 2])
+      date: new Date(2018, 5, 2)
     }, {
-      date: moment([2018, 5, 3]),
+      date: new Date(2018, 5, 3),
       bleeding: {
         value: 2
       }
     }, {
-      date: moment([2018, 5, 4])
+      date: new Date(2018, 5, 4)
     }, {
-      date: moment([2018, 5, 9]),
+      date: new Date(2018, 5, 9),
       bleeding: {
         value: 2,
         exclude: true
       }
     }, {
-      date: moment([2018, 5, 10]),
+      date: new Date(2018, 5, 10),
       bleeding: {
         value: 2,
         exclude: true
       }
     }]
-    const targetDate = moment([2018, 5, 17])
+    const targetDate = new Date(2018, 5, 17)
     const result = getCycleDayNumber(cycleDays, targetDate)
     expect(result).to.eql(15)
   })
 
   it('gets the correct number if the target day is not in the current cycle', () => {
     const cycleDays = [{
-      date: moment([2018, 5, 14]),
+      date: new Date(2018, 5, 14),
     }, {
-      date: moment([2018, 5, 13]),
+      date: new Date(2018, 5, 13),
       bleeding: {
         value: 2
       }
     }, {
-      date: moment([2018, 4, 12]),
+      date: new Date(2018, 4, 12),
     }, {
-      date: moment([2018, 4, 11]),
+      date: new Date(2018, 4, 11),
       bleeding: {
         value: 2
       }
     }, {
-      date: moment([2018, 4, 10]),
+      date: new Date(2018, 4, 10),
       bleeding: {
         value: 2
       }
     }, {
-      date: moment([2018, 4, 9]),
+      date: new Date(2018, 4, 9),
     }]
 
-    const targetDate = moment([2018, 4, 27])
+    const targetDate = new Date(2018, 4, 27)
     const result = getCycleDayNumber(cycleDays, targetDate)
     expect(result).to.eql(18)
   })
@@ -177,22 +176,22 @@ describe('getCycleDay returns null', () => {
   const getCycleDayNumber = getCycleDayNumberModule()
   it('if there are no bleeding days', function () {
     const cycleDays = [{
-      date: moment([2018, 5, 2])
+      date: new Date(2018, 5, 2)
     }, {
-      date: moment([2018, 5, 4])
+      date: new Date(2018, 5, 4)
     }, {
-      date: moment([2018, 5, 9]),
+      date: new Date(2018, 5, 9),
     }, {
-      date: moment([2018, 5, 10]),
+      date: new Date(2018, 5, 10),
     }]
-    const targetDate = moment([2018, 5, 17])
+    const targetDate = new Date(2018, 5, 17)
     const result = getCycleDayNumber(cycleDays, targetDate)
     expect(result).to.be.null()
   })
 
   it('if there are no cycle days', function () {
     const cycleDays = []
-    const targetDate = moment([2018, 5, 17])
+    const targetDate = new Date(2018, 5, 17)
     const result = getCycleDayNumber(cycleDays, targetDate)
     expect(result).to.be.null()
   })
@@ -205,35 +204,35 @@ describe('getCycleDay with cycle thresholds', () => {
 
   it('disregards bleeding breaks shorter than the min cycle threshold in a bleeding period', () => {
     const cycleDays = [{
-      date: moment([2018, 5, 10]),
+      date: new Date(2018, 5, 10),
       bleeding: {
         value: 2
       }
     }, {
-      date: moment([2018, 5, 14]),
+      date: new Date(2018, 5, 14),
       bleeding: {
         value: 2
       }
     }]
 
-    const targetDate = moment([2018, 5, 17])
+    const targetDate = new Date(2018, 5, 17)
     const result = getCycleDayNumber(cycleDays, targetDate)
     expect(result).to.eql(8)
   })
 
   it('counts bleeding breaks longer than the min cycle threshold in a bleeding period', () => {
     const cycleDays = [{
-      date: moment([2018, 5, 9]),
+      date: new Date(2018, 5, 9),
       bleeding: {
         value: 2
       }
     }, {
-      date: moment([2018, 5, 14]),
+      date: new Date(2018, 5, 14),
       bleeding: {
         value: 2
       }
     }]
-    const targetDate = moment([2018, 5, 17])
+    const targetDate = new Date(2018, 5, 17)
     const result = getCycleDayNumber(cycleDays, targetDate)
     expect(result).to.eql(4)
   })