diff --git a/get-cycle-day-number.js b/get-cycle-day-number.js
index 30b56b8..75014a8 100644
--- a/get-cycle-day-number.js
+++ b/get-cycle-day-number.js
@@ -1,46 +1,44 @@
-export default function (cycleDays, targetDay) {
-  const lastFirstBleedingday = findLastFirstBleedingDay(cycleDays)
+import moment from 'moment'
 
-  if (!lastFirstBleedingday) return
+export default function config(opts) {
+  opts = opts || {
+    // at the very minimum, a cycle can be a bleeding day
+    // followed by a non-bleeding day, thus a length of 2
+    minCycleLengthInDays: 2
+  }
 
-  const diffInDays = targetDay.diff(lastFirstBleedingday.date, 'days')
+  return function getCycleDayNumber(unsorted, targetDate) {
+    // sort the cycle days in descending order so we travel into
+    // the past as we iterate over the array
+    const cycleDays = [...unsorted].sort((a, b) => b.date.isAfter(a.date))
 
-  // cycle starts at day 1
-  return diffInDays + 1
-}
+    const lastPeriodStart = cycleDays.find((day, i) => {
+      if (
+        isBleedingDay(day) &&
+        thereIsNoPreviousBleedingDayWithinTheThreshold(day, cycleDays.slice(i + 1), opts.minCycleLengthInDays)) {
+        return true
+      }
+    })
 
-function findLastFirstBleedingDay(cycleDays) {
-  // sort the cycle days in descending order
-  // so we travel into the past as we iterate
-  // over the array
-  cycleDays.sort((a,b) => b.date - a.date)
+    if (!lastPeriodStart) return null
 
-  let sawBleeding = false
+    // by default, moment.diff rounds down, so we get the decimal number
+    // and round it ourselves
+    const diffInDays = Math.round(targetDate.diff(lastPeriodStart.date, 'days', true))
 
-  for (let i = 0; i < cycleDays.length; i++) {
-    const cycleDay = cycleDays[i]
-
-    // we have detected the day before the beginning
-    // of a bleeding period, so the previous cycle day in the array
-    // was the first day of bleeding
-    if (sawBleeding && (!isBleedingDay(cycleDay))) {
-      return cycleDays[i - 1]
-    }
-
-    // if we get to the earliest cycle day and there was
-    // bleeding on that day, it's the first bleeding day for us
-    if (i === cycleDays.length - 1 && isBleedingDay(cycleDay)) {
-      return cycleDay
-    }
-
-    if (isBleedingDay(cycleDay)) {
-      sawBleeding = true
-    }
+    // cycle starts at day 1
+    return diffInDays + 1
   }
 }
 
-function isBleedingDay(cycleDay) {
-  return cycleDay.bleeding
-    && cycleDay.bleeding.value
-    && !cycleDay.bleeding.exclude
+function thereIsNoPreviousBleedingDayWithinTheThreshold(bleedingDay, earlierCycleDays, threshold) {
+  // the bleeding day itself is included in the threshold, thus we subtract 1
+  const minCycleThresholdDate = moment(bleedingDay.date).subtract(threshold - 1, 'days')
+  return !earlierCycleDays.some(day => {
+    return day.date.isSameOrAfter(minCycleThresholdDate, 'day') && isBleedingDay(day)
+  })
+}
+
+function isBleedingDay(day) {
+  return day.bleeding && day.bleeding.value && !day.bleeding.exclude
 }
\ No newline at end of file
diff --git a/package-lock.json b/package-lock.json
index 9cedc1c..c531614 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -2766,6 +2766,12 @@
       "integrity": "sha512-A46qtFgd+g7pDZinpnwiRJtxbC1hpgf0uzP3iG89scHk0AUC7A1TGxf5OiiOUv/JMZR8GOt8hL900hV0bOy5xA==",
       "dev": true
     },
+    "dirty-chai": {
+      "version": "2.0.1",
+      "resolved": "https://registry.npmjs.org/dirty-chai/-/dirty-chai-2.0.1.tgz",
+      "integrity": "sha512-ys79pWKvDMowIDEPC6Fig8d5THiC0DJ2gmTeGzVAoEH18J8OzLud0Jh7I9IWg3NSk8x2UocznUuFmfHCXYZx9w==",
+      "dev": true
+    },
     "doctrine": {
       "version": "2.1.0",
       "resolved": "https://registry.npmjs.org/doctrine/-/doctrine-2.1.0.tgz",
diff --git a/package.json b/package.json
index aa857af..28310a9 100644
--- a/package.json
+++ b/package.json
@@ -26,6 +26,7 @@
   "devDependencies": {
     "babel-preset-react-native": "4.0.0",
     "chai": "^4.1.2",
+    "dirty-chai": "^2.0.1",
     "eslint": "^4.19.1",
     "eslint-plugin-react": "^7.8.2",
     "mocha": "^5.2.0",
diff --git a/test/get-cycle-day.spec.js b/test/get-cycle-day.spec.js
index a7d3a1f..32eefd2 100644
--- a/test/get-cycle-day.spec.js
+++ b/test/get-cycle-day.spec.js
@@ -1,10 +1,15 @@
-import { expect } from 'chai'
+import chai from 'chai'
+import dirtyChai from 'dirty-chai'
 import moment from 'moment'
 
-import getCycleDayNumber from '../get-cycle-day-number'
+const expect = chai.expect
+chai.use(dirtyChai)
 
-describe('getCycleDay returns the cycle day', () => {
-  it('if the last data entered is a bleeding day', function () {
+import getCycleDayNumberModule from '../get-cycle-day-number'
+
+describe('getCycleDay', () => {
+  const getCycleDayNumber = getCycleDayNumberModule()
+  it('works if the last data entered is a bleeding day', function () {
     const cycleDays = [{
       date: moment([2018, 5, 2])
     }, {
@@ -30,7 +35,7 @@ describe('getCycleDay returns the cycle day', () => {
     expect(result).to.eql(9)
   })
 
-  it('if the last data entered is a non-bleeding day', function () {
+  it('works if the last data entered is a non-bleeding day', function () {
     const cycleDays = [{
       date: moment([2018, 5, 2])
     }, {
@@ -90,10 +95,10 @@ describe('getCycleDay returns the cycle day', () => {
 
     const targetDate = moment([2018, 5, 17])
     const result = getCycleDayNumber(cycleDays, targetDate)
-    expect(result).to.eql(9)
+    expect(result).to.eql(5)
   })
 
-  it('if there are only bleeding days', function () {
+  it('works when there are only bleeding days', function () {
     const cycleDays = [{
       date: moment([2018, 5, 9]),
       bleeding: {
@@ -110,7 +115,7 @@ describe('getCycleDay returns the cycle day', () => {
     expect(result).to.eql(9)
   })
 
-  it('if some bleedings are exluded', function () {
+  it('works if some bleedings are exluded', function () {
     const cycleDays = [{
       date: moment([2018, 5, 2])
     }, {
@@ -139,7 +144,8 @@ describe('getCycleDay returns the cycle day', () => {
   })
 })
 
-describe('getCycleDay returns undefined', () => {
+describe('getCycleDay returns null', () => {
+  const getCycleDayNumber = getCycleDayNumberModule()
   it('if there are no bleeding days', function () {
     const cycleDays = [{
       date: moment([2018, 5, 2])
@@ -152,13 +158,54 @@ describe('getCycleDay returns undefined', () => {
     }]
     const targetDate = moment([2018, 5, 17])
     const result = getCycleDayNumber(cycleDays, targetDate)
-    expect(result).to.be.undefined
+    expect(result).to.be.null()
   })
 
   it('if there are no cycle days', function () {
     const cycleDays = []
     const targetDate = moment([2018, 5, 17])
     const result = getCycleDayNumber(cycleDays, targetDate)
-    expect(result).to.be.undefined
+    expect(result).to.be.null()
+  })
+})
+
+describe('getCycleDay with cycle thresholds', () => {
+  const getCycleDayNumber = getCycleDayNumberModule({
+    minCycleLengthInDays: 5
+  })
+
+  it('disregards bleeding breaks shorter than the min cycle threshold in a bleeding period', () => {
+    const cycleDays = [{
+      date: moment([2018, 5, 10]),
+      bleeding: {
+        value: 2
+      }
+    }, {
+      date: moment([2018, 5, 14]),
+      bleeding: {
+        value: 2
+      }
+    }]
+
+    const targetDate = moment([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]),
+      bleeding: {
+        value: 2
+      }
+    }, {
+      date: moment([2018, 5, 14]),
+      bleeding: {
+        value: 2
+      }
+    }]
+    const targetDate = moment([2018, 5, 17])
+    const result = getCycleDayNumber(cycleDays, targetDate)
+    expect(result).to.eql(4)
   })
 })
\ No newline at end of file