EventValidator: RRULE repairing inserts unwanted COUNT=-1 (#53)57-exception-when-unknown-timezone-in-calendar-provider

* EventValidator.sameTypeForDtStartAndRruleUntil: fix COUNT=-1 problem, add tests
* Tests
* EventValidator: always set UNTIL to UTC
* Move util classes; add TimeZone.toZoneIdCompat() tests
* Optimize imports

33 files changed, 191 insertions, 96 deletions

diff --git a/src/androidTest/java/at/bitfire/ical4android/AndroidCalendarTest.kt b/src/androidTest/java/at/bitfire/ical4android/AndroidCalendarTest.kt
index a8ab2f4..dbd9c4c 100644
--- a/src/androidTest/java/at/bitfire/ical4android/AndroidCalendarTest.kt
+++ b/src/androidTest/java/at/bitfire/ical4android/AndroidCalendarTest.kt
@@ -14,10 +14,10 @@ import android.provider.CalendarContract.Calendars
 import android.provider.CalendarContract.Colors
 import androidx.test.platform.app.InstrumentationRegistry
 import androidx.test.rule.GrantPermissionRule
-import at.bitfire.ical4android.MiscUtils.ContentProviderClientHelper.closeCompat
-import at.bitfire.ical4android.MiscUtils.UriHelper.asSyncAdapter
 import at.bitfire.ical4android.impl.TestCalendar
 import at.bitfire.ical4android.impl.TestEvent
+import at.bitfire.ical4android.util.MiscUtils.ContentProviderClientHelper.closeCompat
+import at.bitfire.ical4android.util.MiscUtils.UriHelper.asSyncAdapter
 import net.fortuna.ical4j.model.property.DtEnd
 import net.fortuna.ical4j.model.property.DtStart
 import org.junit.*
diff --git a/src/androidTest/java/at/bitfire/ical4android/AndroidEventTest.kt b/src/androidTest/java/at/bitfire/ical4android/AndroidEventTest.kt
index c9ff0b2..556fa0b 100644
--- a/src/androidTest/java/at/bitfire/ical4android/AndroidEventTest.kt
+++ b/src/androidTest/java/at/bitfire/ical4android/AndroidEventTest.kt
@@ -13,11 +13,12 @@ import android.net.Uri
 import android.provider.CalendarContract.*
 import androidx.test.platform.app.InstrumentationRegistry.getInstrumentation
 import androidx.test.rule.GrantPermissionRule
-import at.bitfire.ical4android.MiscUtils.ContentProviderClientHelper.closeCompat
-import at.bitfire.ical4android.MiscUtils.UriHelper.asSyncAdapter
 import at.bitfire.ical4android.impl.TestCalendar
 import at.bitfire.ical4android.impl.TestEvent
 import at.bitfire.ical4android.util.AndroidTimeUtils
+import at.bitfire.ical4android.util.DateUtils
+import at.bitfire.ical4android.util.MiscUtils.ContentProviderClientHelper.closeCompat
+import at.bitfire.ical4android.util.MiscUtils.UriHelper.asSyncAdapter
 import net.fortuna.ical4j.model.*
 import net.fortuna.ical4j.model.component.VAlarm
 import net.fortuna.ical4j.model.parameter.*
diff --git a/src/androidTest/java/at/bitfire/ical4android/AndroidTaskTest.kt b/src/androidTest/java/at/bitfire/ical4android/AndroidTaskTest.kt
index c907439..61565cb 100644
--- a/src/androidTest/java/at/bitfire/ical4android/AndroidTaskTest.kt
+++ b/src/androidTest/java/at/bitfire/ical4android/AndroidTaskTest.kt
@@ -12,6 +12,7 @@ import android.net.Uri
 import androidx.test.filters.MediumTest
 import at.bitfire.ical4android.impl.TestTask
 import at.bitfire.ical4android.impl.TestTaskList
+import at.bitfire.ical4android.util.DateUtils
 import net.fortuna.ical4j.model.Date
 import net.fortuna.ical4j.model.DateList
 import net.fortuna.ical4j.model.DateTime
diff --git a/src/androidTest/java/at/bitfire/ical4android/AndroidTimeZonesTest.kt b/src/androidTest/java/at/bitfire/ical4android/AndroidTimeZonesTest.kt
index d51c1ad..d6199ad 100644
--- a/src/androidTest/java/at/bitfire/ical4android/AndroidTimeZonesTest.kt
+++ b/src/androidTest/java/at/bitfire/ical4android/AndroidTimeZonesTest.kt
@@ -4,6 +4,7 @@
 
 package at.bitfire.ical4android
 
+import at.bitfire.ical4android.util.DateUtils
 import org.junit.Assert
 import org.junit.Assert.assertNotNull
 import org.junit.Test
diff --git a/src/androidTest/java/at/bitfire/ical4android/AospTest.kt b/src/androidTest/java/at/bitfire/ical4android/AospTest.kt
index bf18803..c048f25 100644
--- a/src/androidTest/java/at/bitfire/ical4android/AospTest.kt
+++ b/src/androidTest/java/at/bitfire/ical4android/AospTest.kt
@@ -12,7 +12,7 @@ import android.net.Uri
 import android.provider.CalendarContract
 import androidx.test.platform.app.InstrumentationRegistry
 import androidx.test.rule.GrantPermissionRule
-import at.bitfire.ical4android.MiscUtils.ContentProviderClientHelper.closeCompat
+import at.bitfire.ical4android.util.MiscUtils.ContentProviderClientHelper.closeCompat
 import org.junit.After
 import org.junit.Assert.assertNotNull
 import org.junit.Before
diff --git a/src/androidTest/java/at/bitfire/ical4android/BatchOperationTest.kt b/src/androidTest/java/at/bitfire/ical4android/BatchOperationTest.kt
index 66310df..4ef3148 100644
--- a/src/androidTest/java/at/bitfire/ical4android/BatchOperationTest.kt
+++ b/src/androidTest/java/at/bitfire/ical4android/BatchOperationTest.kt
@@ -13,9 +13,9 @@ import android.provider.CalendarContract
 import androidx.test.filters.FlakyTest
 import androidx.test.platform.app.InstrumentationRegistry
 import androidx.test.rule.GrantPermissionRule
-import at.bitfire.ical4android.MiscUtils.ContentProviderClientHelper.closeCompat
 import at.bitfire.ical4android.impl.TestCalendar
 import at.bitfire.ical4android.impl.TestEvent
+import at.bitfire.ical4android.util.MiscUtils.ContentProviderClientHelper.closeCompat
 import net.fortuna.ical4j.model.property.Attendee
 import net.fortuna.ical4j.model.property.DtEnd
 import net.fortuna.ical4j.model.property.DtStart
diff --git a/src/androidTest/java/at/bitfire/ical4android/EventTest.kt b/src/androidTest/java/at/bitfire/ical4android/EventTest.kt
index f114bf3..e016b07 100644
--- a/src/androidTest/java/at/bitfire/ical4android/EventTest.kt
+++ b/src/androidTest/java/at/bitfire/ical4android/EventTest.kt
@@ -4,6 +4,7 @@
 
 package at.bitfire.ical4android
 
+import at.bitfire.ical4android.util.DateUtils
 import net.fortuna.ical4j.model.Date
 import net.fortuna.ical4j.model.DateTime
 import net.fortuna.ical4j.model.Parameter
diff --git a/src/androidTest/java/at/bitfire/ical4android/ICalendarTest.kt b/src/androidTest/java/at/bitfire/ical4android/ICalendarTest.kt
index ee0b944..a62fb72 100644
--- a/src/androidTest/java/at/bitfire/ical4android/ICalendarTest.kt
+++ b/src/androidTest/java/at/bitfire/ical4android/ICalendarTest.kt
@@ -4,6 +4,7 @@
 
 package at.bitfire.ical4android
 
+import at.bitfire.ical4android.util.DateUtils
 import net.fortuna.ical4j.data.CalendarBuilder
 import net.fortuna.ical4j.model.Component
 import net.fortuna.ical4j.model.Date
diff --git a/src/androidTest/java/at/bitfire/ical4android/JtxCollectionTest.kt b/src/androidTest/java/at/bitfire/ical4android/JtxCollectionTest.kt
index 29b5157..3e9f886 100644
--- a/src/androidTest/java/at/bitfire/ical4android/JtxCollectionTest.kt
+++ b/src/androidTest/java/at/bitfire/ical4android/JtxCollectionTest.kt
@@ -9,8 +9,8 @@ import android.content.ContentProviderClient
 import android.content.ContentValues
 import androidx.test.platform.app.InstrumentationRegistry
 import androidx.test.rule.GrantPermissionRule
-import at.bitfire.ical4android.MiscUtils.ContentProviderClientHelper.closeCompat
 import at.bitfire.ical4android.impl.TestJtxCollection
+import at.bitfire.ical4android.util.MiscUtils.ContentProviderClientHelper.closeCompat
 import at.techbee.jtx.JtxContract
 import at.techbee.jtx.JtxContract.asSyncAdapter
 import junit.framework.TestCase.*
diff --git a/src/androidTest/java/at/bitfire/ical4android/JtxICalObjectTest.kt b/src/androidTest/java/at/bitfire/ical4android/JtxICalObjectTest.kt
index f82c07d..e0cb10a 100644
--- a/src/androidTest/java/at/bitfire/ical4android/JtxICalObjectTest.kt
+++ b/src/androidTest/java/at/bitfire/ical4android/JtxICalObjectTest.kt
@@ -11,8 +11,8 @@ import android.database.DatabaseUtils
 import android.os.ParcelFileDescriptor
 import androidx.test.platform.app.InstrumentationRegistry
 import androidx.test.rule.GrantPermissionRule
-import at.bitfire.ical4android.MiscUtils.ContentProviderClientHelper.closeCompat
 import at.bitfire.ical4android.impl.TestJtxCollection
+import at.bitfire.ical4android.util.MiscUtils.ContentProviderClientHelper.closeCompat
 import at.techbee.jtx.JtxContract
 import at.techbee.jtx.JtxContract.JtxICalObject
 import at.techbee.jtx.JtxContract.JtxICalObject.Component
diff --git a/src/androidTest/java/at/bitfire/ical4android/TaskTest.kt b/src/androidTest/java/at/bitfire/ical4android/TaskTest.kt
index cbe0bcc..f9f72af 100644
--- a/src/androidTest/java/at/bitfire/ical4android/TaskTest.kt
+++ b/src/androidTest/java/at/bitfire/ical4android/TaskTest.kt
@@ -4,6 +4,7 @@
 
 package at.bitfire.ical4android
 
+import at.bitfire.ical4android.util.DateUtils
 import net.fortuna.ical4j.model.*
 import net.fortuna.ical4j.model.component.VAlarm
 import net.fortuna.ical4j.model.parameter.RelType
diff --git a/src/androidTest/java/at/bitfire/ical4android/impl/TestJtxCollection.kt b/src/androidTest/java/at/bitfire/ical4android/impl/TestJtxCollection.kt
index 5a69060..2bef306 100644
--- a/src/androidTest/java/at/bitfire/ical4android/impl/TestJtxCollection.kt
+++ b/src/androidTest/java/at/bitfire/ical4android/impl/TestJtxCollection.kt
@@ -9,7 +9,7 @@ import android.content.ContentProviderClient
 import at.bitfire.ical4android.JtxCollection
 import at.bitfire.ical4android.JtxCollectionFactory
 import at.bitfire.ical4android.JtxICalObject
-import at.bitfire.ical4android.MiscUtils.CursorHelper.toValues
+import at.bitfire.ical4android.util.MiscUtils.CursorHelper.toValues
 import at.techbee.jtx.JtxContract
 import java.util.*
 
diff --git a/src/androidTest/java/at/bitfire/ical4android/AndroidTimeUtilsTest.kt b/src/androidTest/java/at/bitfire/ical4android/util/AndroidTimeUtilsTest.kt
index 9cb7653..18a37f9 100644
--- a/src/androidTest/java/at/bitfire/ical4android/AndroidTimeUtilsTest.kt
+++ b/src/androidTest/java/at/bitfire/ical4android/util/AndroidTimeUtilsTest.kt
@@ -2,9 +2,8 @@
  * Copyright © All Contributors. See LICENSE and AUTHORS in the root directory for details.
  **************************************************************************************************/
 
-package at.bitfire.ical4android
+package at.bitfire.ical4android.util
 
-import at.bitfire.ical4android.util.AndroidTimeUtils
 import net.fortuna.ical4j.data.CalendarBuilder
 import net.fortuna.ical4j.model.*
 import net.fortuna.ical4j.model.component.VTimeZone
diff --git a/src/androidTest/java/at/bitfire/ical4android/DateUtilsTest.kt b/src/androidTest/java/at/bitfire/ical4android/util/DateUtilsTest.kt
index 395b8da..fe1f468 100644
--- a/src/androidTest/java/at/bitfire/ical4android/DateUtilsTest.kt
+++ b/src/androidTest/java/at/bitfire/ical4android/util/DateUtilsTest.kt
@@ -2,7 +2,7 @@
  * Copyright © All Contributors. See LICENSE and AUTHORS in the root directory for details.
  **************************************************************************************************/
 
-package at.bitfire.ical4android
+package at.bitfire.ical4android.util
 
 import net.fortuna.ical4j.model.Date
 import net.fortuna.ical4j.model.DateTime
diff --git a/src/androidTest/java/at/bitfire/ical4android/MiscUtilsAndroidTest.kt b/src/androidTest/java/at/bitfire/ical4android/util/MiscUtilsTest.kt
index d6f7e40..dee8dd9 100644
--- a/src/androidTest/java/at/bitfire/ical4android/MiscUtilsAndroidTest.kt
+++ b/src/androidTest/java/at/bitfire/ical4android/util/MiscUtilsTest.kt
@@ -2,20 +2,20 @@
  * Copyright © All Contributors. See LICENSE and AUTHORS in the root directory for details.
  **************************************************************************************************/
 
-package at.bitfire.ical4android
+package at.bitfire.ical4android.util
 
 import android.accounts.Account
 import android.content.ContentValues
 import android.database.MatrixCursor
 import android.net.Uri
 import androidx.test.filters.SmallTest
-import at.bitfire.ical4android.MiscUtils.CursorHelper.toValues
-import at.bitfire.ical4android.MiscUtils.UriHelper.asSyncAdapter
+import at.bitfire.ical4android.util.MiscUtils.CursorHelper.toValues
+import at.bitfire.ical4android.util.MiscUtils.UriHelper.asSyncAdapter
 import org.junit.Assert
 import org.junit.Assert.assertEquals
 import org.junit.Test
 
-class MiscUtilsAndroidTest {
+class MiscUtilsTest {
 
     private val tzVienna = DateUtils.ical4jTimeZone("Europe/Vienna")
 
diff --git a/src/androidTest/java/at/bitfire/ical4android/TimeApiExtensionsTest.kt b/src/androidTest/java/at/bitfire/ical4android/util/TimeApiExtensionsTest.kt
index 44a02a0..e5c6fc0 100644
--- a/src/androidTest/java/at/bitfire/ical4android/TimeApiExtensionsTest.kt
+++ b/src/androidTest/java/at/bitfire/ical4android/util/TimeApiExtensionsTest.kt
@@ -2,7 +2,7 @@
  * Copyright © All Contributors. See LICENSE and AUTHORS in the root directory for details.
  **************************************************************************************************/
 
-package at.bitfire.ical4android
+package at.bitfire.ical4android.util
 
 import at.bitfire.ical4android.util.TimeApiExtensions.requireTimeZone
 import at.bitfire.ical4android.util.TimeApiExtensions.toDuration
@@ -28,7 +28,18 @@ class TimeApiExtensionsTest {
 
 
     @Test
-    fun testDateToLocalDate() {
+    fun testTimeZone_toZoneIdCompat_NotUtc() {
+        assertEquals(ZoneId.of("Europe/Berlin"), tzBerlin.toZoneId())
+    }
+
+    @Test
+    fun testTimeZone_toZoneIdCompat_Utc() {
+        assertEquals(ZoneOffset.UTC, TimeZones.getUtcTimeZone().toZoneIdCompat())
+    }
+
+
+    @Test
+    fun testDate_toLocalDate() {
         val date = Date("20200620").toLocalDate()
         assertEquals(2020, date.year)
         assertEquals(6, date.monthValue)
@@ -38,19 +49,19 @@ class TimeApiExtensionsTest {
 
 
     @Test
-    fun testDateTimeRequireTimeZone() {
+    fun testDateTime_requireTimeZone() {
         val time = DateTime("2020707T010203", tzBerlin)
         assertEquals(tzBerlin, time.requireTimeZone())
     }
 
     @Test
-    fun testDateTimeRequireTimeZone_Floating() {
+    fun testDateTime_requireTimeZone_Floating() {
         val time = DateTime("2020707T010203")
         assertEquals(TimeZone.getDefault(), time.requireTimeZone())
     }
 
     @Test
-    fun testDateTimeRequireTimeZone_Utc() {
+    fun testDateTime_requireTimeZone_Utc() {
         val time = DateTime("2020707T010203Z").apply { isUtc = true }
         assertTrue(time.isUtc)
         assertEquals(TimeZones.getUtcTimeZone(), time.requireTimeZone())
@@ -58,7 +69,7 @@ class TimeApiExtensionsTest {
 
 
     @Test
-    fun testDateTimeToLocalDate_TimezoneBoundary() {
+    fun testDateTime_toLocalDate_TimezoneBoundary() {
         val date = DateTime("20200620T000000", tzBerlin).toLocalDate()
         assertEquals(2020, date.year)
         assertEquals(6, date.monthValue)
@@ -67,7 +78,7 @@ class TimeApiExtensionsTest {
     }
 
     @Test
-    fun testDateTimeToLocalDate_TimezoneDuringDay() {
+    fun testDateTime_toLocalDate_TimezoneDuringDay() {
         val date = DateTime("20200620T123000", tzBerlin).toLocalDate()
         assertEquals(2020, date.year)
         assertEquals(6, date.monthValue)
@@ -76,7 +87,7 @@ class TimeApiExtensionsTest {
     }
 
     @Test
-    fun testDateTimeToLocalDate_UtcDuringDay() {
+    fun testDateTime_toLocalDate_UtcDuringDay() {
         val date = DateTime("20200620T123000Z").apply { isUtc = true }.toLocalDate()
         assertEquals(2020, date.year)
         assertEquals(6, date.monthValue)
@@ -86,23 +97,23 @@ class TimeApiExtensionsTest {
 
 
     @Test
-    fun testDateTimeToLocalTime() {
+    fun testDateTime_toLocalTime() {
         assertEquals(LocalTime.of(12, 30), DateTime("20200620T123000", tzBerlin).toLocalTime())
     }
 
     @Test
-    fun testDateTimeToLocalTime_Floating() {
+    fun testDateTime_toLocalTime_Floating() {
         assertEquals(LocalTime.of(12, 30), DateTime("20200620T123000").toLocalTime())
     }
 
     @Test
-    fun testDateTimeToLocalTime_Utc() {
+    fun testDateTime_toLocalTime_Utc() {
         assertEquals(LocalTime.of(12, 30), DateTime("20200620T123000Z").apply { isUtc = true }.toLocalTime())
     }
 
 
     @Test
-    fun testDateTimeToZonedDateTime() {
+    fun testDateTime_toZonedDateTime() {
         assertEquals(
                 ZonedDateTime.of(2020, 7, 7, 10, 30, 0, 0, tzBerlin.toZoneIdCompat()),
                 DateTime("20200707T103000", tzBerlin).toZonedDateTime()
@@ -110,7 +121,7 @@ class TimeApiExtensionsTest {
     }
 
     @Test
-    fun testDateTimeToZonedDateTime_Floating() {
+    fun testDateTime_toZonedDateTime_Floating() {
         assertEquals(
                 ZonedDateTime.of(2020, 7, 7, 10, 30, 0, 0, ZoneId.systemDefault()),
                 DateTime("20200707T103000").toZonedDateTime()
@@ -118,7 +129,7 @@ class TimeApiExtensionsTest {
     }
 
     @Test
-    fun testDateTimeToZonedDateTime_UTC() {
+    fun testDateTime_toZonedDateTime_UTC() {
         assertEquals(
                 ZonedDateTime.of(2020, 7, 7, 10, 30, 0, 0, ZoneOffset.UTC),
                 DateTime("20200707T103000Z").apply { isUtc = true }.toZonedDateTime()
@@ -127,31 +138,31 @@ class TimeApiExtensionsTest {
 
 
     @Test
-    fun testLocalDateToIcal4jDate() {
+    fun testLocalDate_toIcal4jDate() {
         assertEquals(Date("19000118"), LocalDate.of(1900, 1, 18).toIcal4jDate())
         assertEquals(Date("20200620"), LocalDate.of(2020, 6, 20).toIcal4jDate())
     }
 
     @Test
-    fun testZonedDateTimeToIcal4jDateTime() {
+    fun testZonedDateTime_toIcal4jDateTime_NotUtc() {
         val tzBerlin = DateUtils.ical4jTimeZone("Europe/Berlin")
         assertEquals(
-                DateTime("20200705T010203", tzBerlin),
-                ZonedDateTime.of(2020, 7, 5, 1, 2, 3, 0, ZoneId.of("Europe/Berlin")).toIcal4jDateTime()
+            DateTime("20200705T010203", tzBerlin),
+            ZonedDateTime.of(2020, 7, 5, 1, 2, 3, 0, ZoneId.of("Europe/Berlin")).toIcal4jDateTime()
         )
     }
 
     @Test
-    fun testZonedDateTimeToIcal4jDateTime_Utc() {
+    fun testZonedDateTime_toIcal4jDateTime_Utc() {
         assertEquals(
-                DateTime("20200705T010203Z"),
-                ZonedDateTime.of(2020, 7, 5, 1, 2, 3, 0, ZoneOffset.UTC).toIcal4jDateTime()
+            DateTime("20200705T010203Z"),
+            ZonedDateTime.of(2020, 7, 5, 1, 2, 3, 0, ZoneOffset.UTC).toIcal4jDateTime()
         )
     }
 
 
     @Test
-    fun testTemporalAmountToDuration() {
+    fun testTemporalAmount_toDuration() {
         assertEquals(Duration.ofHours(1), Duration.ofHours(1).toDuration(Instant.EPOCH))
         assertEquals(Duration.ofDays(1), Duration.ofDays(1).toDuration(Instant.EPOCH))
         assertEquals(Duration.ofDays(1), Period.ofDays(1).toDuration(Instant.EPOCH))
@@ -161,7 +172,7 @@ class TimeApiExtensionsTest {
     }
 
     @Test
-    fun testTemporalAmountToRfc5545Duration_Duration() {
+    fun testTemporalAmount_toRfc5545Duration_Duration() {
         assertEquals("P0S", Duration.ofDays(0).toRfc5545Duration(Instant.EPOCH))
         assertEquals("P2W", Duration.ofDays(14).toRfc5545Duration(Instant.EPOCH))
         assertEquals("P15D", Duration.ofDays(15).toRfc5545Duration(Instant.EPOCH))
diff --git a/src/androidTest/java/at/bitfire/ical4android/validation/EventValidatorTest.kt b/src/androidTest/java/at/bitfire/ical4android/validation/EventValidatorTest.kt
index 2af3fe8..fa3d959 100644
--- a/src/androidTest/java/at/bitfire/ical4android/validation/EventValidatorTest.kt
+++ b/src/androidTest/java/at/bitfire/ical4android/validation/EventValidatorTest.kt
@@ -6,14 +6,12 @@ package at.bitfire.ical4android.validation
 
 import at.bitfire.ical4android.Event
 import at.bitfire.ical4android.InvalidCalendarException
-import net.fortuna.ical4j.model.Date
-import net.fortuna.ical4j.model.DateTime
-import net.fortuna.ical4j.model.Recur
-import net.fortuna.ical4j.model.TimeZoneRegistryFactory
+import net.fortuna.ical4j.model.*
 import net.fortuna.ical4j.model.property.DtEnd
 import net.fortuna.ical4j.model.property.DtStart
 import net.fortuna.ical4j.model.property.RRule
 import org.junit.Assert.*
+import org.junit.Assume
 import org.junit.Test
 import java.io.StringReader
 
@@ -79,10 +77,10 @@ class EventValidatorTest {
             rRules.add(RRule("FREQ=MONTHLY;UNTIL=20251214T001100Z"))      // DATETIME (UTC)
         }
         assertEquals(DateTime("20211115T001100Z"), event.dtStart!!.date)
-        assertEquals(DateTime("20251214T001100Z"), event.rRules.first.recur.until)
+        assertEquals("FREQ=MONTHLY;UNTIL=20251214T001100Z", event.rRules.joinToString())
         EventValidator.sameTypeForDtStartAndRruleUntil(event.dtStart!!, event.rRules)
         assertEquals(DateTime("20211115T001100Z"), event.dtStart!!.date)
-        assertEquals(DateTime("20251214T001100Z"), event.rRules.first.recur.until)
+        assertEquals("FREQ=MONTHLY;UNTIL=20251214T001100Z", event.rRules.joinToString())
 
         val event1 = Event.eventsFromReader(StringReader(
             "BEGIN:VCALENDAR\n" +
@@ -92,7 +90,7 @@ class EventValidatorTest {
                "RRULE:FREQ=MONTHLY;UNTIL=20231214;BYMONTHDAY=15\n" +           // DATE
                "END:VEVENT\n" +
                "END:VCALENDAR")).first()
-        assertEquals(Date("20231214"), event1.rRules.first.recur.until)
+        assertEquals("FREQ=MONTHLY;UNTIL=20231214;BYMONTHDAY=15", event1.rRules.joinToString())
 
         val event2 = Event.eventsFromReader(StringReader(
             "BEGIN:VCALENDAR\n" +
@@ -102,7 +100,7 @@ class EventValidatorTest {
                "RRULE:FREQ=YEARLY;UNTIL=20230216;BYMONTHDAY=15\n" +            // DATE
                "END:VEVENT\n" +
                "END:VCALENDAR")).first()
-        assertEquals(Date("20230216"), event2.rRules.first.recur.until)
+        assertEquals("FREQ=YEARLY;UNTIL=20230216;BYMONTHDAY=15", event2.rRules.joinToString())
     }
 
     @Test
@@ -119,7 +117,7 @@ class EventValidatorTest {
             event.rRules.first.recur.until
         )
         EventValidator.sameTypeForDtStartAndRruleUntil(event.dtStart!!, event.rRules)
-        assertEquals(Date("20211214"), event.rRules.first.recur.until)
+        assertEquals("FREQ=MONTHLY;UNTIL=20211214", event.rRules.joinToString())
 
         val event1 = Event.eventsFromReader(
             StringReader(
@@ -133,7 +131,7 @@ class EventValidatorTest {
             )
         ).first()
         assertEquals(1639440000000, event1.rRules.first.recur.until.time)
-        assertEquals(Date("20211214"), event1.rRules.first.recur.until)
+        assertEquals("FREQ=MONTHLY;UNTIL=20211214;BYMONTHDAY=15", event1.rRules.joinToString())
     }
 
     @Test
@@ -150,22 +148,22 @@ class EventValidatorTest {
         // As it does not happen often, for the sake of simplicity we just accept either
         EventValidator.sameTypeForDtStartAndRruleUntil(event2.dtStart!!, event2.rRules)
         assertTrue(
-            Date("20230218") == event2.rRules.first.recur.until ||
-            Date("20230217") == event2.rRules.first.recur.until
+            "FREQ=YEARLY;UNTIL=20230218;BYMONTHDAY=15" == event2.rRules.joinToString() ||
+            "FREQ=YEARLY;UNTIL=20230217;BYMONTHDAY=15" == event2.rRules.joinToString()
         )
     }
 
     @Test
-    fun testSameTypeForDtStartAndRruleUntil_DtStartIsDateTimeAndRruleUntilIsDate() {
+    fun testSameTypeForDtStartAndRruleUntil_DtStartIsDateTimeWithTzAndRruleUntilIsDate() {
         // should add (possibly missing) time in UNTIL if DTSTART value is of type DATETIME (not just DATE)
 
         val event = Event().apply {
             dtStart = DtStart(DateTime("20110605T001100Z"))         // DATETIME (UTC)
             rRules.add(RRule("FREQ=MONTHLY;UNTIL=20211214"))        // DATE
         }
-        assertEquals(Date("20211214"), event.rRules.first.recur.until)
+        assertEquals("FREQ=MONTHLY;UNTIL=20211214", event.rRules.joinToString())
         EventValidator.sameTypeForDtStartAndRruleUntil(event.dtStart!!, event.rRules)
-        assertEquals(DateTime("20211214T001100Z"), event.rRules.first.recur.until)
+        assertEquals("FREQ=MONTHLY;UNTIL=20211214T001100Z", event.rRules.joinToString())
 
         val event1 = Event.eventsFromReader(StringReader(
             "BEGIN:VCALENDAR\n" +
@@ -175,17 +173,34 @@ class EventValidatorTest {
                 "RRULE:FREQ=MONTHLY;UNTIL=20211214;BYMONTHDAY=15\n" +   // DATE
                 "END:VEVENT\n" +
                 "END:VCALENDAR")).first()
-        assertEquals(DateTime("20211214T053000", tzReg.getTimeZone("America/New_York")), event1.rRules.first.recur.until)
+        assertEquals("FREQ=MONTHLY;UNTIL=20211214T103000Z;BYMONTHDAY=15", event1.rRules.joinToString())
+    }
 
-        val event2 = Event.eventsFromReader(StringReader(
-            "BEGIN:VCALENDAR\n" +
-                "BEGIN:VEVENT\n" +
-                "UID:381fb26b-2da5-4dd2-94d7-2e0874128aa7\n" +
-                "DTSTART;VALUE=DATETIME:20080214T001100\n" +            // DATETIME (no timezone)
-                "RRULE:FREQ=YEARLY;UNTIL=20110214;BYMONTHDAY=15\n" +    // DATE
-                "END:VEVENT\n" +
-                "END:VCALENDAR")).first()
-        assertEquals(DateTime("20110214T001100"), event2.rRules.first.recur.until)
+    @Test
+    fun testSameTypeForDtStartAndRruleUntil_DtStartIsDateTimeWithoutTzAndRruleUntilIsDate() {
+        // should add (possibly missing) time in UNTIL if DTSTART value is of type DATETIME (not just DATE)
+
+        val event = Event().apply {
+            dtStart = DtStart(DateTime("20110605T001100Z"))         // DATETIME (UTC)
+            rRules.add(RRule("FREQ=MONTHLY;UNTIL=20211214"))        // DATE
+        }
+        assertEquals("FREQ=MONTHLY;UNTIL=20211214", event.rRules.joinToString())
+        EventValidator.sameTypeForDtStartAndRruleUntil(event.dtStart!!, event.rRules)
+        assertEquals("FREQ=MONTHLY;UNTIL=20211214T001100Z", event.rRules.joinToString())
+
+        Assume.assumeTrue(TimeZone.getDefault().id == "Europe/Vienna")
+        val event2 = Event.eventsFromReader(
+            StringReader(
+                "BEGIN:VCALENDAR\n" +
+                        "BEGIN:VEVENT\n" +
+                        "UID:381fb26b-2da5-4dd2-94d7-2e0874128aa7\n" +
+                        "DTSTART;VALUE=DATETIME:20080214T001100\n" +            // DATETIME (no timezone)
+                        "RRULE:FREQ=YEARLY;UNTIL=20110214;BYMONTHDAY=15\n" +    // DATE
+                        "END:VEVENT\n" +
+                        "END:VCALENDAR"
+            )
+        ).first()
+        assertEquals("FREQ=YEARLY;UNTIL=20110213T231100Z;BYMONTHDAY=15", event2.rRules.joinToString())
     }
 
 
@@ -311,4 +326,10 @@ class EventValidatorTest {
         ), rrules.toTypedArray())
     }
 
+
+    // helpers
+
+    private fun Iterable<RRule>.joinToString(): String =
+        this.map { rRule -> rRule.value }.joinToString("\n")
+
 }
\ No newline at end of file
diff --git a/src/main/java/at/bitfire/ical4android/AndroidCalendar.kt b/src/main/java/at/bitfire/ical4android/AndroidCalendar.kt
index 398da20..aa92e57 100644
--- a/src/main/java/at/bitfire/ical4android/AndroidCalendar.kt
+++ b/src/main/java/at/bitfire/ical4android/AndroidCalendar.kt
@@ -10,8 +10,8 @@ import android.content.ContentUris
 import android.content.ContentValues
 import android.net.Uri
 import android.provider.CalendarContract.*
-import at.bitfire.ical4android.MiscUtils.CursorHelper.toValues
-import at.bitfire.ical4android.MiscUtils.UriHelper.asSyncAdapter
+import at.bitfire.ical4android.util.MiscUtils.CursorHelper.toValues
+import at.bitfire.ical4android.util.MiscUtils.UriHelper.asSyncAdapter
 import java.io.FileNotFoundException
 import java.util.*
 import java.util.logging.Level
diff --git a/src/main/java/at/bitfire/ical4android/AndroidEvent.kt b/src/main/java/at/bitfire/ical4android/AndroidEvent.kt
index 4230ee0..8648dd5 100644
--- a/src/main/java/at/bitfire/ical4android/AndroidEvent.kt
+++ b/src/main/java/at/bitfire/ical4android/AndroidEvent.kt
@@ -14,9 +14,11 @@ import android.provider.CalendarContract.*
 import android.util.Patterns
 import androidx.annotation.CallSuper
 import at.bitfire.ical4android.BatchOperation.CpoBuilder
-import at.bitfire.ical4android.MiscUtils.CursorHelper.toValues
-import at.bitfire.ical4android.MiscUtils.UriHelper.asSyncAdapter
 import at.bitfire.ical4android.util.AndroidTimeUtils
+import at.bitfire.ical4android.util.DateUtils
+import at.bitfire.ical4android.util.MiscUtils
+import at.bitfire.ical4android.util.MiscUtils.CursorHelper.toValues
+import at.bitfire.ical4android.util.MiscUtils.UriHelper.asSyncAdapter
 import at.bitfire.ical4android.util.TimeApiExtensions
 import at.bitfire.ical4android.util.TimeApiExtensions.requireZoneId
 import at.bitfire.ical4android.util.TimeApiExtensions.toIcal4jDate
@@ -25,7 +27,6 @@ import at.bitfire.ical4android.util.TimeApiExtensions.toLocalDate
 import at.bitfire.ical4android.util.TimeApiExtensions.toLocalTime
 import at.bitfire.ical4android.util.TimeApiExtensions.toRfc5545Duration
 import at.bitfire.ical4android.util.TimeApiExtensions.toZonedDateTime
-import at.bitfire.ical4android.validation.EventValidator
 import net.fortuna.ical4j.model.*
 import net.fortuna.ical4j.model.Date
 import net.fortuna.ical4j.model.component.VAlarm
@@ -780,10 +781,11 @@ abstract class AndroidEvent(
             builder .withValue(Events.DURATION, duration?.toRfc5545Duration(dtStart.date.toInstant()))
                     .withValue(Events.DTEND, null)
 
-            // add RRULe
-            if (event.rRules.isNotEmpty())
-                builder.withValue(Events.RRULE, event.rRules.joinToString(AndroidTimeUtils.RECURRENCE_RULE_SEPARATOR) { it.value })
-            else
+            // add RRULEs
+            if (event.rRules.isNotEmpty()) {
+                builder.withValue(Events.RRULE, event.rRules
+                    .joinToString(AndroidTimeUtils.RECURRENCE_RULE_SEPARATOR) { it.value })
+            } else
                 builder.withValue(Events.RRULE, null)
 
             if (event.rDates.isNotEmpty()) {
diff --git a/src/main/java/at/bitfire/ical4android/AndroidTask.kt b/src/main/java/at/bitfire/ical4android/AndroidTask.kt
index 84af609..3e56dc1 100644
--- a/src/main/java/at/bitfire/ical4android/AndroidTask.kt
+++ b/src/main/java/at/bitfire/ical4android/AndroidTask.kt
@@ -10,8 +10,10 @@ import android.net.Uri
 import android.os.RemoteException
 import androidx.annotation.CallSuper
 import at.bitfire.ical4android.BatchOperation.CpoBuilder
-import at.bitfire.ical4android.MiscUtils.CursorHelper.toValues
 import at.bitfire.ical4android.util.AndroidTimeUtils
+import at.bitfire.ical4android.util.DateUtils
+import at.bitfire.ical4android.util.MiscUtils
+import at.bitfire.ical4android.util.MiscUtils.CursorHelper.toValues
 import net.fortuna.ical4j.model.*
 import net.fortuna.ical4j.model.Date
 import net.fortuna.ical4j.model.TimeZone
diff --git a/src/main/java/at/bitfire/ical4android/AndroidTaskList.kt b/src/main/java/at/bitfire/ical4android/AndroidTaskList.kt
index 8439d80..01215fe 100644
--- a/src/main/java/at/bitfire/ical4android/AndroidTaskList.kt
+++ b/src/main/java/at/bitfire/ical4android/AndroidTaskList.kt
@@ -8,8 +8,8 @@ import android.accounts.Account
 import android.content.ContentUris
 import android.content.ContentValues
 import android.net.Uri
-import at.bitfire.ical4android.MiscUtils.CursorHelper.toValues
-import at.bitfire.ical4android.MiscUtils.UriHelper.asSyncAdapter
+import at.bitfire.ical4android.util.MiscUtils.CursorHelper.toValues
+import at.bitfire.ical4android.util.MiscUtils.UriHelper.asSyncAdapter
 import org.dmfs.tasks.contract.TaskContract
 import org.dmfs.tasks.contract.TaskContract.Property.Relation
 import org.dmfs.tasks.contract.TaskContract.TaskLists
diff --git a/src/main/java/at/bitfire/ical4android/Event.kt b/src/main/java/at/bitfire/ical4android/Event.kt
index 3f2e567..7c6449b 100644
--- a/src/main/java/at/bitfire/ical4android/Event.kt
+++ b/src/main/java/at/bitfire/ical4android/Event.kt
@@ -4,8 +4,8 @@
 
 package at.bitfire.ical4android
 
-import at.bitfire.ical4android.DateUtils.isDateTime
 import at.bitfire.ical4android.ICalendar.Companion.CALENDAR_NAME
+import at.bitfire.ical4android.util.DateUtils.isDateTime
 import at.bitfire.ical4android.validation.EventValidator
 import net.fortuna.ical4j.data.CalendarOutputter
 import net.fortuna.ical4j.data.ParserException
diff --git a/src/main/java/at/bitfire/ical4android/ICalendar.kt b/src/main/java/at/bitfire/ical4android/ICalendar.kt
index 678b195..c519278 100644
--- a/src/main/java/at/bitfire/ical4android/ICalendar.kt
+++ b/src/main/java/at/bitfire/ical4android/ICalendar.kt
@@ -4,6 +4,7 @@
 
 package at.bitfire.ical4android
 
+import at.bitfire.ical4android.util.MiscUtils
 import at.bitfire.ical4android.validation.ICalPreprocessor
 import net.fortuna.ical4j.data.CalendarBuilder
 import net.fortuna.ical4j.data.ParserException
diff --git a/src/main/java/at/bitfire/ical4android/JtxCollection.kt b/src/main/java/at/bitfire/ical4android/JtxCollection.kt
index 1527ef5..dc920be 100644
--- a/src/main/java/at/bitfire/ical4android/JtxCollection.kt
+++ b/src/main/java/at/bitfire/ical4android/JtxCollection.kt
@@ -10,7 +10,7 @@ import android.content.ContentUris
 import android.content.ContentValues
 import android.content.Context
 import android.net.Uri
-import at.bitfire.ical4android.MiscUtils.CursorHelper.toValues
+import at.bitfire.ical4android.util.MiscUtils.CursorHelper.toValues
 import at.techbee.jtx.JtxContract
 import at.techbee.jtx.JtxContract.asSyncAdapter
 import net.fortuna.ical4j.model.Calendar
diff --git a/src/main/java/at/bitfire/ical4android/JtxICalObject.kt b/src/main/java/at/bitfire/ical4android/JtxICalObject.kt
index 91d53ed..fd17ed9 100644
--- a/src/main/java/at/bitfire/ical4android/JtxICalObject.kt
+++ b/src/main/java/at/bitfire/ical4android/JtxICalObject.kt
@@ -10,7 +10,7 @@ import android.net.ParseException
 import android.net.Uri
 import android.os.ParcelFileDescriptor
 import android.util.Base64
-import at.bitfire.ical4android.MiscUtils.CursorHelper.toValues
+import at.bitfire.ical4android.util.MiscUtils.CursorHelper.toValues
 import at.techbee.jtx.JtxContract
 import at.techbee.jtx.JtxContract.JtxICalObject.TZ_ALLDAY
 import at.techbee.jtx.JtxContract.asSyncAdapter
diff --git a/src/main/java/at/bitfire/ical4android/Task.kt b/src/main/java/at/bitfire/ical4android/Task.kt
index 0e70ca0..b19e1c6 100644
--- a/src/main/java/at/bitfire/ical4android/Task.kt
+++ b/src/main/java/at/bitfire/ical4android/Task.kt
@@ -5,6 +5,7 @@
 package at.bitfire.ical4android
 
 import androidx.annotation.IntRange
+import at.bitfire.ical4android.util.DateUtils
 import net.fortuna.ical4j.data.CalendarOutputter
 import net.fortuna.ical4j.data.ParserException
 import net.fortuna.ical4j.model.*
diff --git a/src/main/java/at/bitfire/ical4android/TaskProvider.kt b/src/main/java/at/bitfire/ical4android/TaskProvider.kt
index 6754388..a9a14e3 100644
--- a/src/main/java/at/bitfire/ical4android/TaskProvider.kt
+++ b/src/main/java/at/bitfire/ical4android/TaskProvider.kt
@@ -9,7 +9,7 @@ import android.content.ContentProviderClient
 import android.content.Context
 import android.content.pm.PackageManager
 import androidx.core.content.pm.PackageInfoCompat
-import at.bitfire.ical4android.MiscUtils.ContentProviderClientHelper.closeCompat
+import at.bitfire.ical4android.util.MiscUtils.ContentProviderClientHelper.closeCompat
 import org.dmfs.tasks.contract.TaskContract
 import java.io.Closeable
 import java.util.logging.Level
diff --git a/src/main/java/at/bitfire/ical4android/util/AndroidTimeUtils.kt b/src/main/java/at/bitfire/ical4android/util/AndroidTimeUtils.kt
index 9d22cd8..337ab41 100644
--- a/src/main/java/at/bitfire/ical4android/util/AndroidTimeUtils.kt
+++ b/src/main/java/at/bitfire/ical4android/util/AndroidTimeUtils.kt
@@ -7,7 +7,6 @@
 package at.bitfire.ical4android.util
 
 import android.text.format.Time
-import at.bitfire.ical4android.DateUtils
 import at.bitfire.ical4android.Ical4Android
 import net.fortuna.ical4j.model.*
 import net.fortuna.ical4j.model.Date
diff --git a/src/main/java/at/bitfire/ical4android/DateUtils.kt b/src/main/java/at/bitfire/ical4android/util/DateUtils.kt
index c9ceffa..6c0060e 100644
--- a/src/main/java/at/bitfire/ical4android/DateUtils.kt
+++ b/src/main/java/at/bitfire/ical4android/util/DateUtils.kt
@@ -2,8 +2,10 @@
  * Copyright © All Contributors. See LICENSE and AUTHORS in the root directory for details.
  **************************************************************************************************/
 
-package at.bitfire.ical4android
+package at.bitfire.ical4android.util
 
+import at.bitfire.ical4android.Ical4Android
+import at.bitfire.ical4android.UsesThreadContextClassLoader
 import net.fortuna.ical4j.data.CalendarBuilder
 import net.fortuna.ical4j.model.Date
 import net.fortuna.ical4j.model.DateTime
diff --git a/src/main/java/at/bitfire/ical4android/MiscUtils.kt b/src/main/java/at/bitfire/ical4android/util/MiscUtils.kt
index 0c76624..76b3e02 100644
--- a/src/main/java/at/bitfire/ical4android/MiscUtils.kt
+++ b/src/main/java/at/bitfire/ical4android/util/MiscUtils.kt
@@ -2,7 +2,7 @@
  * Copyright © All Contributors. See LICENSE and AUTHORS in the root directory for details.
  **************************************************************************************************/
 
-package at.bitfire.ical4android
+package at.bitfire.ical4android.util
 
 import android.accounts.Account
 import android.content.ContentProviderClient
diff --git a/src/main/java/at/bitfire/ical4android/util/TimeApiExtensions.kt b/src/main/java/at/bitfire/ical4android/util/TimeApiExtensions.kt
index f9b1ac1..9ff5529 100644
--- a/src/main/java/at/bitfire/ical4android/util/TimeApiExtensions.kt
+++ b/src/main/java/at/bitfire/ical4android/util/TimeApiExtensions.kt
@@ -4,7 +4,6 @@
 
 package at.bitfire.ical4android.util
 
-import at.bitfire.ical4android.DateUtils
 import net.fortuna.ical4j.model.Date
 import net.fortuna.ical4j.model.DateTime
 import net.fortuna.ical4j.util.TimeZones
@@ -31,8 +30,15 @@ object TimeApiExtensions {
 
     /**
      * [TimeZone.toZoneId] can't be used with the current desugaring library yet!
+     *
+     * @return [ZoneId] of the time zone; [ZoneOffset.UTC] if the time zone equals to [TimeZones.getUtcTimeZone]
      */
-    fun TimeZone.toZoneIdCompat(): ZoneId = ZoneId.of(id)
+    fun TimeZone.toZoneIdCompat(): ZoneId {
+        return if (this == TimeZones.getUtcTimeZone())
+            ZoneOffset.UTC
+        else
+            ZoneId.of(id)
+    }
 
 
     /***** Dates *****/
@@ -69,6 +75,15 @@ object TimeApiExtensions {
         return Date(cal)
     }
 
+    /**
+     * Converts this zoned date-time (date/time with specific time zone) to an
+     * ical4j [DateTime] object.
+     *
+     * Sets UTC flag ([DateTime.isUtc], means `...ThhmmddZ` format) when this zone-date time object has a
+     * time zone of [ZoneOffset.UTC].
+     *
+     * @return ical4j [DateTime] of the given zoned date-time
+     */
     fun ZonedDateTime.toIcal4jDateTime(): DateTime {
         val date = DateTime(toEpochSecond() * MILLIS_PER_SECOND)
         if (zone == ZoneOffset.UTC)
diff --git a/src/main/java/at/bitfire/ical4android/validation/EventValidator.kt b/src/main/java/at/bitfire/ical4android/validation/EventValidator.kt
index d8ee48c..71e6147 100644
--- a/src/main/java/at/bitfire/ical4android/validation/EventValidator.kt
+++ b/src/main/java/at/bitfire/ical4android/validation/EventValidator.kt
@@ -4,15 +4,15 @@
 
 package at.bitfire.ical4android.validation
 
-import at.bitfire.ical4android.DateUtils
 import at.bitfire.ical4android.Event
 import at.bitfire.ical4android.Ical4Android
 import at.bitfire.ical4android.InvalidCalendarException
+import at.bitfire.ical4android.util.DateUtils
 import at.bitfire.ical4android.util.TimeApiExtensions.toIcal4jDate
-import at.bitfire.ical4android.util.TimeApiExtensions.toIcal4jDateTime
 import at.bitfire.ical4android.util.TimeApiExtensions.toLocalDate
 import at.bitfire.ical4android.util.TimeApiExtensions.toZoneIdCompat
 import net.fortuna.ical4j.model.DateTime
+import net.fortuna.ical4j.model.Recur
 import net.fortuna.ical4j.model.property.DtStart
 import net.fortuna.ical4j.model.property.RRule
 import net.fortuna.ical4j.util.TimeZones
@@ -52,16 +52,36 @@ class EventValidator(val e: Event) {
          */
         internal fun sameTypeForDtStartAndRruleUntil(dtStart: DtStart, rRules: MutableList<RRule>) {
             if (DateUtils.isDate(dtStart)) {
-                for (rRule in rRules) {
+                // DTSTART is a DATE
+                val newRRules = mutableListOf<RRule>()
+                val rRuleIterator = rRules.iterator()
+                while (rRuleIterator.hasNext()) {
+                    val rRule = rRuleIterator.next()
                     rRule.recur.until?.let { until ->
                         if (until is DateTime) {
                             Ical4Android.log.warning("DTSTART has DATE, but UNTIL has DATETIME; making UNTIL have DATE only")
-                            rRule.recur.until = until.toLocalDate().toIcal4jDate()
+
+                            val newUntil = until.toLocalDate().toIcal4jDate()
+
+                            // remove current RRULE and remember new one to be added
+                            val newRRule = RRule(Recur.Builder(rRule.recur)
+                                .until(newUntil)
+                                .build())
+                            Ical4Android.log.info("New $newRRule (was ${rRule.toString().trim()})")
+                            newRRules += newRRule
+                            rRuleIterator.remove()
                         }
                     }
                 }
+                // add repaired RRULEs
+                rRules += newRRules
+
             } else if (DateUtils.isDateTime(dtStart)) {
-                for (rRule in rRules) {
+                // DTSTART is a DATE-TIME
+                val newRRules = mutableListOf<RRule>()
+                val rRuleIterator = rRules.iterator()
+                while (rRuleIterator.hasNext()) {
+                    val rRule = rRuleIterator.next()
                     rRule.recur.until?.let { until ->
                         if (until !is DateTime) {
                             Ical4Android.log.warning("DTSTART has DATETIME, but UNTIL has DATE; copying time from DTSTART to UNTIL")
@@ -81,15 +101,30 @@ class EventValidator(val e: Event) {
                                 dtStartCal.get(Calendar.SECOND)
                             )
 
-                            rRule.recur.until =
-                                ZonedDateTime.of(
-                                    until.toLocalDate(),    // date from until
-                                    dtStartTime,       // time from dtStart
-                                    dtStartTimeZone.toZoneIdCompat()
-                                ).toIcal4jDateTime()
+                            val newUntil = ZonedDateTime.of(
+                                until.toLocalDate(),    // date from until
+                                dtStartTime,       // time from dtStart
+                                dtStartTimeZone.toZoneIdCompat()
+                            )
+
+                            // Android requires UNTIL in UTC as defined in RFC 2445.
+                            // https://android.googlesource.com/platform/frameworks/opt/calendar/+/refs/tags/android-12.1.0_r27/src/com/android/calendarcommon2/RecurrenceProcessor.java#93
+                            val newUntilUTC = DateTime(true).apply {
+                                time = newUntil.toInstant().toEpochMilli()
+                            }
+
+                            // remove current RRULE and remember new one to be added
+                            val newRRule = RRule(Recur.Builder(rRule.recur)
+                                .until(newUntilUTC)
+                                .build())
+                            Ical4Android.log.info("New $newRRule (was ${rRule.toString().trim()})")
+                            newRRules += newRRule
+                            rRuleIterator.remove()
                         }
                     }
                 }
+                // add repaired RRULEs
+                rRules += newRRules
             } else
                 throw InvalidCalendarException("Event with invalid DTSTART value")
         }
diff --git a/src/test/java/at/bitfire/ical4android/MiscUtilsTest.kt b/src/test/java/at/bitfire/ical4android/MiscUtilsTest.kt
index e32ba0a..c9cf19d 100644
--- a/src/test/java/at/bitfire/ical4android/MiscUtilsTest.kt
+++ b/src/test/java/at/bitfire/ical4android/MiscUtilsTest.kt
@@ -4,6 +4,7 @@
 
 package at.bitfire.ical4android
 
+import at.bitfire.ical4android.util.MiscUtils
 import org.junit.Assert.assertTrue
 import org.junit.Test