Properly handle all-day event timezone switch

app/src/main/kotlin/com/simplemobiletools/calendar/pro/activities/EventActivity.kt

@@ -161,7 +161,7 @@ class EventActivity : SimpleActivity() {
         event_end_time.setOnClickListener { setupEndTime() }
         event_time_zone.setOnClickListener { setupTimeZone() }
 
-        event_all_day.setOnCheckedChangeListener { compoundButton, isChecked -> toggleAllDay(isChecked) }
+        event_all_day.setOnCheckedChangeListener { _, isChecked -> toggleAllDay(isChecked) }
         event_repetition.setOnClickListener { showRepeatIntervalDialog() }
         event_repetition_rule_holder.setOnClickListener { showRepetitionRuleDialog() }
         event_repetition_limit_holder.setOnClickListener { showRepetitionTypePicker() }
@@ -213,7 +213,7 @@ class EventActivity : SimpleActivity() {
 
         event_type_holder.setOnClickListener { showEventTypeDialog() }
         event_all_day.apply {
-            isChecked = mEvent.flags and FLAG_ALL_DAY != 0
+            isChecked = mEvent.getIsAllDay()
             jumpDrawablesToCurrentState()
         }
 
@@ -227,13 +227,6 @@ class EventActivity : SimpleActivity() {
         showOrHideTimeZone()
     }
 
-    private fun showOrHideTimeZone() {
-        val allowChangingTimeZones = config.allowChangingTimeZones && !event_all_day.isChecked
-        event_time_zone_divider.beVisibleIf(allowChangingTimeZones)
-        event_time_zone_image.beVisibleIf(allowChangingTimeZones)
-        event_time_zone.beVisibleIf(allowChangingTimeZones)
-    }
-
     private fun refreshMenuItems() {
         if (::mEvent.isInitialized) {
             event_toolbar.menu.apply {
@@ -258,17 +251,25 @@ class EventActivity : SimpleActivity() {
     }
 
     private fun getStartEndTimes(): Pair<Long, Long> {
-        val offset = if (!config.allowChangingTimeZones || mEvent.getTimeZoneString().equals(mOriginalTimeZone, true)) {
+        if (mIsAllDayEvent) {
-            0
+            val newStartTS = mEventStartDateTime.withTimeAtStartOfDay().seconds()
+            val newEndTS = mEventEndDateTime.withTimeAtStartOfDay().withHourOfDay(12).seconds()
+            return Pair(newStartTS, newEndTS)
         } else {
-            val original = if (mOriginalTimeZone.isEmpty()) DateTimeZone.getDefault().id else mOriginalTimeZone
+            val offset = if (!config.allowChangingTimeZones || mEvent.getTimeZoneString().equals(mOriginalTimeZone, true)) {
-            val millis = System.currentTimeMillis()
+                0
-            (DateTimeZone.forID(mEvent.getTimeZoneString()).getOffset(millis) - DateTimeZone.forID(original).getOffset(millis)) / 1000L
+            } else {
-        }
+                val original = mOriginalTimeZone.ifEmpty { DateTimeZone.getDefault().id }
+                val millis = System.currentTimeMillis()
+                val newOffset = DateTimeZone.forID(mEvent.getTimeZoneString()).getOffset(millis)
+                val oldOffset = DateTimeZone.forID(original).getOffset(millis)
+                (newOffset - oldOffset) / 1000L
+            }
 
-        val newStartTS = mEventStartDateTime.seconds() - offset
+            val newStartTS = mEventStartDateTime.seconds() - offset
-        val newEndTS = mEventEndDateTime.seconds() - offset
+            val newEndTS = mEventEndDateTime.seconds() - offset
-        return Pair(newStartTS, newEndTS)
+            return Pair(newStartTS, newEndTS)
+        }
     }
 
     private fun getReminders(): ArrayList<Reminder> {
@@ -309,6 +310,7 @@ class EventActivity : SimpleActivity() {
             mRepeatRule != mEvent.repeatRule ||
             mEventTypeId != mEvent.eventType ||
             mWasCalendarChanged ||
+            mIsAllDayEvent != mEvent.getIsAllDay() ||
             hasTimeChanged
         ) {
             return true
@@ -998,17 +1000,23 @@ class EventActivity : SimpleActivity() {
         }
     }
 
-    private fun toggleAllDay(isChecked: Boolean) {
+    private fun toggleAllDay(isAllDay: Boolean) {
-        mIsAllDayEvent = isChecked
         hideKeyboard()
-        event_start_time.beGoneIf(isChecked)
+        mIsAllDayEvent = isAllDay
-        event_end_time.beGoneIf(isChecked)
+        event_start_time.beGoneIf(isAllDay)
-        mEvent.timeZone = if (isChecked) DateTimeZone.UTC.id else DateTimeZone.getDefault().id
+        event_end_time.beGoneIf(isAllDay)
         updateTimeZoneText()
         showOrHideTimeZone()
         resetTime()
     }
 
+    private fun showOrHideTimeZone() {
+        val allowChangingTimeZones = config.allowChangingTimeZones && !mIsAllDayEvent
+        event_time_zone_divider.beVisibleIf(allowChangingTimeZones)
+        event_time_zone_image.beVisibleIf(allowChangingTimeZones)
+        event_time_zone.beVisibleIf(allowChangingTimeZones)
+    }
+
     private fun shareEvent() {
         shareEvents(arrayListOf(mEvent.id!!))
     }
@@ -1157,11 +1165,7 @@ class EventActivity : SimpleActivity() {
             reminder3Type = mReminder3Type
             repeatInterval = mRepeatInterval
             importId = newImportId
-            timeZone = when {
+            timeZone = if (mIsAllDayEvent || timeZone.isEmpty()) DateTimeZone.getDefault().id else timeZone
-                mIsAllDayEvent -> DateTimeZone.UTC.id
-                timeZone.isEmpty() -> DateTimeZone.getDefault().id
-                else -> timeZone
-            }
             flags = mEvent.flags.addBitIf(event_all_day.isChecked, FLAG_ALL_DAY)
             repeatLimit = if (repeatInterval == 0) 0 else mRepeatLimit
             repeatRule = mRepeatRule
@@ -1195,7 +1199,7 @@ class EventActivity : SimpleActivity() {
     }
 
     private fun storeEvent(wasRepeatable: Boolean) {
-        if (mEvent.id == null || mEvent.id == null) {
+        if (mEvent.id == null) {
             eventsHelper.insertEvent(mEvent, addToCalDAV = true, showToasts = true) {
                 hideKeyboard()
 

app/src/main/kotlin/com/simplemobiletools/calendar/pro/extensions/Event.kt

@@ -0,0 +1,30 @@
+package com.simplemobiletools.calendar.pro.extensions
+
+import com.simplemobiletools.calendar.pro.helpers.Formatter
+import com.simplemobiletools.calendar.pro.helpers.TWELVE_HOURS
+import com.simplemobiletools.calendar.pro.models.Event
+import org.joda.time.DateTimeZone
+
+/** Shifts all-day events to local timezone such that the event starts and ends on the same time as in UTC */
+fun Event.toLocalAllDayEvent() {
+    require(this.getIsAllDay()) { "Must be an all day event!" }
+
+    timeZone = DateTimeZone.getDefault().id
+    startTS = Formatter.getShiftedLocalTS(startTS)
+    endTS = Formatter.getShiftedLocalTS(endTS)
+    if (endTS > startTS) {
+        endTS -= TWELVE_HOURS
+    }
+}
+
+/** Shifts all-day events to UTC such that the event starts on the same time in UTC too */
+fun Event.toUtcAllDayEvent() {
+    require(getIsAllDay()) { "Must be an all day event!" }
+
+    if (endTS >= startTS) {
+        endTS += TWELVE_HOURS
+    }
+    timeZone = DateTimeZone.UTC.id
+    startTS = Formatter.getShiftedUtcTS(startTS)
+    endTS = Formatter.getShiftedUtcTS(endTS)
+}

app/src/main/kotlin/com/simplemobiletools/calendar/pro/helpers/CalDAVHelper.kt

@@ -227,18 +227,14 @@ class CalDAVHelper(val context: Context) {
             val repeatRule = Parser().parseRepeatInterval(rrule, startTS)
             val event = Event(
                 null, startTS, endTS, title, location, description, reminder1?.minutes ?: REMINDER_OFF,
-                reminder2?.minutes ?: REMINDER_OFF, reminder3?.minutes ?: REMINDER_OFF, reminder1?.type
+                reminder2?.minutes ?: REMINDER_OFF, reminder3?.minutes ?: REMINDER_OFF,
-                ?: REMINDER_NOTIFICATION, reminder2?.type ?: REMINDER_NOTIFICATION, reminder3?.type
+                reminder1?.type ?: REMINDER_NOTIFICATION, reminder2?.type ?: REMINDER_NOTIFICATION,
-                ?: REMINDER_NOTIFICATION, repeatRule.repeatInterval, repeatRule.repeatRule,
+                reminder3?.type ?: REMINDER_NOTIFICATION, repeatRule.repeatInterval, repeatRule.repeatRule,
                 repeatRule.repeatLimit, ArrayList(), attendees, importId, eventTimeZone, allDay, eventTypeId, source = source, availability = availability
             )
 
             if (event.getIsAllDay()) {
-                event.startTS = Formatter.getShiftedImportTimestamp(event.startTS)
+                event.toLocalAllDayEvent()
-                event.endTS = Formatter.getShiftedImportTimestamp(event.endTS)
-                if (event.endTS > event.startTS) {
-                    event.endTS -= DAY
-                }
             }
 
             fetchedEventIds.add(importId)
@@ -402,9 +398,6 @@ class CalDAVHelper(val context: Context) {
             put(Events.CALENDAR_ID, event.getCalDAVCalendarId())
             put(Events.TITLE, event.title)
             put(Events.DESCRIPTION, event.description)
-            put(Events.DTSTART, event.startTS * 1000L)
-            put(Events.ALL_DAY, if (event.getIsAllDay()) 1 else 0)
-            put(Events.EVENT_TIMEZONE, event.getTimeZoneString())
             put(Events.EVENT_LOCATION, event.location)
             put(Events.STATUS, Events.STATUS_CONFIRMED)
             put(Events.AVAILABILITY, event.availability)
@@ -416,9 +409,15 @@ class CalDAVHelper(val context: Context) {
                 put(Events.RRULE, repeatRule)
             }
 
-            if (event.getIsAllDay() && event.endTS >= event.startTS)
+            if (event.getIsAllDay()) {
-                event.endTS += DAY
+                event.toUtcAllDayEvent()
+                put(Events.ALL_DAY, 1)
+            } else {
+                put(Events.ALL_DAY, 0)
+            }
 
+            put(Events.DTSTART, event.startTS * 1000L)
+            put(Events.EVENT_TIMEZONE, event.getTimeZoneString())
             if (event.repeatInterval > 0) {
                 put(Events.DURATION, getDurationCode(event))
                 putNull(Events.DTEND)

app/src/main/kotlin/com/simplemobiletools/calendar/pro/helpers/Constants.kt

@@ -53,6 +53,7 @@ const val DEFAULT_START_TIME_CURRENT_TIME = -2
 const val TYPE_EVENT = 0
 const val TYPE_TASK = 1
 
+const val TWELVE_HOURS = 43200
 const val DAY = 86400
 const val WEEK = 604800
 const val MONTH = 2592001    // exact value not taken into account, Joda is used for adding months and years

app/src/main/kotlin/com/simplemobiletools/calendar/pro/helpers/Formatter.kt

@@ -135,7 +135,11 @@ object Formatter {
 
     fun getUTCDayCodeFromTS(ts: Long) = getUTCDateTimeFromTS(ts).toString(DAYCODE_PATTERN)
 
-    fun getShiftedImportTimestamp(ts: Long) = getUTCDateTimeFromTS(ts).withTime(13, 0, 0, 0).withZoneRetainFields(DateTimeZone.getDefault()).seconds()
-
     fun getYearFromDayCode(dayCode: String) = getDateTimeFromCode(dayCode).toString(YEAR_PATTERN)
+
+    fun getShiftedTS(dateTime: DateTime, toZone: DateTimeZone) = dateTime.withTimeAtStartOfDay().withZoneRetainFields(toZone).seconds()
+
+    fun getShiftedLocalTS(ts: Long) = getShiftedTS(dateTime = getUTCDateTimeFromTS(ts), toZone = DateTimeZone.getDefault())
+
+    fun getShiftedUtcTS(ts: Long) = getShiftedTS(dateTime = getDateTimeFromTS(ts), toZone = DateTimeZone.UTC)
 }

app/src/main/kotlin/com/simplemobiletools/calendar/pro/helpers/IcsExporter.kt

@@ -4,7 +4,9 @@ import android.provider.CalendarContract.Events
 import com.simplemobiletools.calendar.pro.R
 import com.simplemobiletools.calendar.pro.extensions.calDAVHelper
 import com.simplemobiletools.calendar.pro.extensions.eventTypesDB
-import com.simplemobiletools.calendar.pro.helpers.IcsExporter.ExportResult.*
+import com.simplemobiletools.calendar.pro.helpers.IcsExporter.ExportResult.EXPORT_FAIL
+import com.simplemobiletools.calendar.pro.helpers.IcsExporter.ExportResult.EXPORT_OK
+import com.simplemobiletools.calendar.pro.helpers.IcsExporter.ExportResult.EXPORT_PARTIAL
 import com.simplemobiletools.calendar.pro.models.CalDAVCalendar
 import com.simplemobiletools.calendar.pro.models.Event
 import com.simplemobiletools.commons.activities.BaseSimpleActivity
@@ -61,7 +63,7 @@ class IcsExporter {
 
                     if (event.getIsAllDay()) {
                         out.writeLn("$DTSTART;$VALUE=$DATE:${Formatter.getDayCodeFromTS(event.startTS)}")
-                        out.writeLn("$DTEND;$VALUE=$DATE:${Formatter.getDayCodeFromTS(event.endTS + DAY)}")
+                        out.writeLn("$DTEND;$VALUE=$DATE:${Formatter.getDayCodeFromTS(event.endTS + TWELVE_HOURS)}")
                     } else {
                         event.startTS.let { out.writeLn("$DTSTART:${Formatter.getExportedTime(it * 1000L)}") }
                         event.endTS.let { out.writeLn("$DTEND:${Formatter.getExportedTime(it * 1000L)}") }

app/src/main/kotlin/com/simplemobiletools/calendar/pro/helpers/IcsImporter.kt

@@ -232,7 +232,7 @@ class IcsImporter(val activity: SimpleActivity) {
                             curRepeatExceptions,
                             "",
                             curImportId,
-                            if (isAllDay) DateTimeZone.UTC.id else DateTimeZone.getDefault().id,
+                            DateTimeZone.getDefault().id,
                             curFlags,
                             curEventTypeId,
                             0,
@@ -242,8 +242,7 @@ class IcsImporter(val activity: SimpleActivity) {
                         )
 
                         if (isAllDay && curEnd > curStart) {
-                            event.endTS -= DAY
+                            event.endTS -= TWELVE_HOURS
-
                             // fix some glitches related to daylight saving shifts
                             if (event.startTS - event.endTS == HOUR_SECONDS.toLong()) {
                                 event.endTS += HOUR_SECONDS

app/src/main/kotlin/com/simplemobiletools/calendar/pro/helpers/Parser.kt

@@ -10,6 +10,7 @@ import com.simplemobiletools.commons.extensions.areDigitsOnly
 import com.simplemobiletools.commons.helpers.*
 import org.joda.time.DateTimeZone
 import org.joda.time.format.DateTimeFormat
+import kotlin.math.floor
 
 class Parser {
     // from RRULE:FREQ=DAILY;COUNT=5 to Daily, 5x...
@@ -101,8 +102,9 @@ class Parser {
         return if (edited.length == 14) {
             parseLongFormat(edited, value.endsWith("Z"))
         } else {
-            val dateTimeFormat = DateTimeFormat.forPattern("yyyyMMdd")
+            val dateTimeFormat = DateTimeFormat.forPattern("yyyyMMdd").withZoneUTC()
-            dateTimeFormat.parseDateTime(edited).withHourOfDay(13).seconds()
+            val dateTime = dateTimeFormat.parseDateTime(edited)
+            Formatter.getShiftedTS(dateTime = dateTime, toZone = DateTimeZone.getDefault())
         }
     }
 
@@ -227,12 +229,12 @@ class Parser {
         var hours = 0
         var remainder = minutes
         if (remainder >= DAY_MINUTES) {
-            days = Math.floor((remainder / DAY_MINUTES).toDouble()).toInt()
+            days = floor((remainder / DAY_MINUTES).toDouble()).toInt()
             remainder -= days * DAY_MINUTES
         }
 
         if (remainder >= 60) {
-            hours = Math.floor((remainder / 60).toDouble()).toInt()
+            hours = floor((remainder / 60).toDouble()).toInt()
             remainder -= hours * 60
         }