diff --git a/components/stats/SymptomOccurance.js b/components/stats/SymptomOccurance.js
index 30dcf89..73388fd 100644
--- a/components/stats/SymptomOccurance.js
+++ b/components/stats/SymptomOccurance.js
@@ -12,15 +12,23 @@ import { Spacing, Typography, Colors } from '../../styles'
 // const { t } = useTranslation(null, { keyPrefix: 'stats' })
 
 const SymptomOccurance = ({ onClose }) => {
-  const data = symOccModule().getCycleStartsOfLastYear()
-  if (!data || data.length === 0) return false
-  console.log('cycle starts:', data)
+  const cycleDays = symOccModule().getCycleStartsOfLastYear()
+  if (!cycleDays || cycleDays.length === 0) return false
+  console.log('cycle starts:', cycleDays)
+
+  const headacheDays = symOccModule().getPainDaysOfLastYear()
+  console.log('pain', headacheDays)
+
+  const cycleDaysOfPain = symOccModule().getCycleDayForPainDays(
+    cycleDays,
+    headacheDays
+  )
+  console.log('cycle days of pain', cycleDaysOfPain)
 
   return (
     <AppModal onClose={onClose}>
       <View>
         <FlatList
-          data={data}
           ListHeaderComponent={FlatListHeader}
           contentContainerStyle={styles.container}
         />
diff --git a/db/index.js b/db/index.js
index f6f2fd0..7d45718 100644
--- a/db/index.js
+++ b/db/index.js
@@ -73,6 +73,9 @@ export function getTemperatureDaysSortedByDate() {
     .filtered('temperature != null')
     .sorted('date', true)
 }
+export function getPainDaysSortedByDate() {
+  return db.objects('CycleDay').filtered('pain != null').sorted('date', true)
+}
 
 export function getCycleDaysSortedByDate() {
   const cycleDays = db.objects('CycleDay').sorted('date', true)
diff --git a/lib/sympto-occurance.js b/lib/sympto-occurance.js
index 1716677..2ffd44e 100644
--- a/lib/sympto-occurance.js
+++ b/lib/sympto-occurance.js
@@ -1,44 +1,70 @@
 import * as joda from '@js-joda/core'
 const LocalDate = joda.LocalDate
-// const DAYS = joda.ChronoUnit.DAYS
+const DAYS = joda.ChronoUnit.DAYS
 
 export default function config(opts) {
   let cycleStartsSortedByDate
+  let painSortedByDate
 
   if (!opts) {
     // we only want to require (and run) the db module
     // when not running the tests
     cycleStartsSortedByDate = require('../db').getCycleStartsSortedByDate()
+    painSortedByDate = require('../db').getPainDaysSortedByDate()
     // maxCycleLength = 45
   } else {
     cycleStartsSortedByDate = opts.cycleStartsSortedByDate || []
+    painSortedByDate = opts.painSortedByDate || []
     // maxCycleLength = opts.maxCycleLength || 99
   }
 
   function getCycleStartsOfLastYear() {
     const today = LocalDate.parse(new Date().toISOString().slice(0, 10))
-    const firstRelevantCycleStart = today.minusYears(1)
+    const firstRelevantDay = today.minusYears(1)
     const relevantCycles = cycleStartsSortedByDate.filter(({ date }) =>
-      LocalDate.parse(date).isAfter(firstRelevantCycleStart)
+      LocalDate.parse(date).isAfter(firstRelevantDay)
     )
     return relevantCycles.map(({ date }) => date)
   }
 
-  function getTodayDate() {
-    return new Date().toISOString().slice(0, 10)
+  function getPainDaysOfLastYear() {
+    const today = LocalDate.parse(new Date().toISOString().slice(0, 10))
+    const firstRelevantDay = today.minusYears(1)
+    const relevantPainDays = painSortedByDate.filter(
+      ({ date, pain }) =>
+        LocalDate.parse(date).isAfter(firstRelevantDay) && pain.headache
+    )
+    return relevantPainDays.map(({ date }) => date)
   }
 
-  const getStats = () =>
-    cycleStartsSortedByDate.map((day, i) => {
-      const today = getTodayDate()
-      return {
-        date: today,
-        k: i,
+  function getCycleDayForPainDays(cycleStarts, painDays) {
+    let i = 0
+    const cycleStartsAsc = cycleStarts.sort().reverse()
+    const painDaysAsc = painDays.sort().reverse()
+    const painCycleDays = painDaysAsc.map((pdate) => {
+      if (LocalDate.parse(pdate).isBefore(LocalDate.parse(cycleStartsAsc[i]))) {
+        // increase index i until cycleStart of this painDay is found
+        for (let j = i + 1; j < cycleStartsAsc.length; j++) {
+          i = j
+          if (
+            !LocalDate.parse(cycleStartsAsc[i]).isAfter(LocalDate.parse(pdate))
+          ) {
+            // not(C > P) === C ≤ P
+            break
+          }
+        }
       }
+      return LocalDate.parse(cycleStartsAsc[i]).until(
+        LocalDate.parse(pdate),
+        DAYS
+      )
     })
+    return painCycleDays
+  }
 
   return {
     getCycleStartsOfLastYear,
-    getStats,
+    getPainDaysOfLastYear,
+    getCycleDayForPainDays,
   }
 }