From bfe00e5bd7c4f1c4304147983e2bdaeee593e46e Mon Sep 17 00:00:00 2001
From: Mike Sheldon <mike@mikeasoft.com>
Date: Thu, 20 Mar 2025 21:24:52 +0000
Subject: [PATCH] Preserve time difference when changing start date (fixes
 #596)

---
 src/views/Event/EditView.vue | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/src/views/Event/EditView.vue b/src/views/Event/EditView.vue
index 931ab2cb9..3e1c5ac47 100644
--- a/src/views/Event/EditView.vue
+++ b/src/views/Event/EditView.vue
@@ -1312,7 +1312,7 @@ watch(endsOn, (newEndsOn) => {
   updateEventDateRelatedToTimezone();
 });
 
-/* 
+/*
 For endsOn, we need to check consistencyBeginsOnBeforeEndsOn() at blur
 because the datetime-local component update itself immediately
 Ex : your event start at 10:00 and stops at 12:00
@@ -1322,9 +1322,18 @@ So you cannot check consistensy in real time, only onBlur because of the moment
 const consistencyBeginsOnBeforeEndsOn = () => {
   // Update endsOn to make sure endsOn is later than beginsOn
   if (endsOn.value && beginsOn.value && endsOn.value <= beginsOn.value) {
-    const newEndsOn = new Date(beginsOn.value);
-    newEndsOn.setUTCHours(beginsOn.value.getUTCHours() + 1);
+    // If the start date has changed, preserve the time difference
+    const newEndsOn = new Date(endsOn.value);
+    newEndsOn.setDate(beginsOn.value.getDate());
+    newEndsOn.setMonth(beginsOn.value.getMonth());
+    newEndsOn.setFullYear(beginsOn.value.getFullYear());
     endsOn.value = newEndsOn;
+    // If the end time is still earlier than the start time set a 1 hour difference
+    if (endsOn.value <= beginsOn.value) {
+      const newEndsOn2 = new Date(beginsOn.value);
+      newEndsOn2.setUTCHours(beginsOn.value.getUTCHours() + 1);
+      endsOn.value = newEndsOn2;
+    }
   }
 };