diff --git a/app/src/main/kotlin/com/simplemobiletools/calendar/pro/activities/EventActivity.kt b/app/src/main/kotlin/com/simplemobiletools/calendar/pro/activities/EventActivity.kt
index a22aaf7ce..e9d11fa60 100644
--- a/app/src/main/kotlin/com/simplemobiletools/calendar/pro/activities/EventActivity.kt
+++ b/app/src/main/kotlin/com/simplemobiletools/calendar/pro/activities/EventActivity.kt
@@ -224,9 +224,14 @@ class EventActivity : SimpleActivity() {
         updateTextColors(event_scrollview)
         updateIconColors()
         refreshMenuItems()
-        event_time_zone_divider.beVisibleIf(config.allowChangingTimeZones)
-        event_time_zone_image.beVisibleIf(config.allowChangingTimeZones)
-        event_time_zone.beVisibleIf(config.allowChangingTimeZones)
+        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() {
@@ -998,6 +1003,9 @@ class EventActivity : SimpleActivity() {
         hideKeyboard()
         event_start_time.beGoneIf(isChecked)
         event_end_time.beGoneIf(isChecked)
+        mEvent.timeZone = if (isChecked) DateTimeZone.UTC.id else DateTimeZone.getDefault().id
+        updateTimeZoneText()
+        showOrHideTimeZone()
         resetTime()
     }
 
@@ -1149,7 +1157,11 @@ class EventActivity : SimpleActivity() {
             reminder3Type = mReminder3Type
             repeatInterval = mRepeatInterval
             importId = newImportId
-            timeZone = if (mEvent.timeZone.isEmpty()) TimeZone.getDefault().id else timeZone
+            timeZone = when {
+                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
diff --git a/app/src/main/kotlin/com/simplemobiletools/calendar/pro/helpers/CalDAVHelper.kt b/app/src/main/kotlin/com/simplemobiletools/calendar/pro/helpers/CalDAVHelper.kt
index 2f4a4de4f..d597c4b33 100644
--- a/app/src/main/kotlin/com/simplemobiletools/calendar/pro/helpers/CalDAVHelper.kt
+++ b/app/src/main/kotlin/com/simplemobiletools/calendar/pro/helpers/CalDAVHelper.kt
@@ -228,8 +228,8 @@ class CalDAVHelper(val context: Context) {
             val event = Event(
                 null, startTS, endTS, title, location, description, reminder1?.minutes ?: REMINDER_OFF,
                 reminder2?.minutes ?: REMINDER_OFF, reminder3?.minutes ?: REMINDER_OFF, reminder1?.type
-                    ?: REMINDER_NOTIFICATION, reminder2?.type ?: REMINDER_NOTIFICATION, reminder3?.type
-                    ?: REMINDER_NOTIFICATION, repeatRule.repeatInterval, repeatRule.repeatRule,
+                ?: REMINDER_NOTIFICATION, reminder2?.type ?: REMINDER_NOTIFICATION, reminder3?.type
+                ?: REMINDER_NOTIFICATION, repeatRule.repeatInterval, repeatRule.repeatRule,
                 repeatRule.repeatLimit, ArrayList(), attendees, importId, eventTimeZone, allDay, eventTypeId, source = source, availability = availability
             )