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 90f07f998..bb29383a9 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
@@ -915,7 +915,8 @@ class EventActivity : SimpleActivity() {
         val offset = if (!config.allowChangingTimeZones || mEvent.getTimeZoneString().equals(mOriginalTimeZone, true)) {
             0
         } else {
-            (DateTimeZone.forID(mEvent.getTimeZoneString()).getOffset(System.currentTimeMillis()) - DateTimeZone.forID(mOriginalTimeZone).getOffset(System.currentTimeMillis())) / 1000L
+            var original = if (mOriginalTimeZone.isEmpty()) DateTimeZone.getDefault().id else mOriginalTimeZone
+            (DateTimeZone.forID(mEvent.getTimeZoneString()).getOffset(System.currentTimeMillis()) - DateTimeZone.forID(original).getOffset(System.currentTimeMillis())) / 1000L
         }
 
         val newStartTS = mEventStartDateTime.withSecondOfMinute(0).withMillisOfSecond(0).seconds() - offset