From 890332f4b6d8445265a73bf48119529f4df75c3d Mon Sep 17 00:00:00 2001
From: Sean Morley <mail@seanmorley.com>
Date: Tue, 13 May 2025 12:50:43 -0400
Subject: [PATCH] Update date validation to use UTC comparison and enhance
 documentation

---
 .../src/lib/components/DateRangeCollapse.svelte     |  4 ++--
 frontend/src/lib/dateUtils.ts                       | 13 +++++++------
 2 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/frontend/src/lib/components/DateRangeCollapse.svelte b/frontend/src/lib/components/DateRangeCollapse.svelte
index 7473772..c1f17bb 100644
--- a/frontend/src/lib/components/DateRangeCollapse.svelte
+++ b/frontend/src/lib/components/DateRangeCollapse.svelte
@@ -366,8 +366,8 @@
 		</div>
 
 		<!-- Validation Message -->
-		{#if !validateDateRange(localStartDate, localEndDate).valid}
-			<div role="alert" class="alert alert-error">
+		{#if !validateDateRange(utcStartDate ?? '', utcEndDate ?? '').valid}
+			<div role="alert" class="alert alert-error mt-2">
 				<svg
 					xmlns="http://www.w3.org/2000/svg"
 					class="h-6 w-6 shrink-0 stroke-current"
diff --git a/frontend/src/lib/dateUtils.ts b/frontend/src/lib/dateUtils.ts
index 166af3b..3eccaa5 100644
--- a/frontend/src/lib/dateUtils.ts
+++ b/frontend/src/lib/dateUtils.ts
@@ -87,10 +87,10 @@ export function updateUTCDate({
 }
 
 /**
- * Validate date ranges
- * @param startDate - Start date string
- * @param endDate - End date string
- * @returns Object with validation result and error message
+ * Validate date ranges using UTC comparison
+ * @param startDate - Start date string in UTC (ISO format)
+ * @param endDate - End date string in UTC (ISO format)
+ * @returns Object with validation result and optional error message
  */
 export function validateDateRange(
 	startDate: string,
@@ -106,11 +106,12 @@ export function validateDateRange(
 	if (
 		startDate &&
 		endDate &&
-		DateTime.fromISO(startDate).toMillis() > DateTime.fromISO(endDate).toMillis()
+		DateTime.fromISO(startDate, { zone: 'utc' }).toMillis() >
+			DateTime.fromISO(endDate, { zone: 'utc' }).toMillis()
 	) {
 		return {
 			valid: false,
-			error: 'Start date must be before end date'
+			error: 'Start date must be before end date (based on UTC)'
 		};
 	}