Update date validation to use UTC comparison and enhance documentation

frontend/src/lib/components/DateRangeCollapse.svelte

@@ -182,6 +182,7 @@
 				<!-- Dual timezone selectors for transportation -->
 				<div class="space-y-4">
 					<div>
+						<!-- svelte-ignore a11y-label-has-associated-control -->
 						<label class="text-sm font-medium block mb-1">
 							{$t('adventures.departure_timezone')}
 						</label>
@@ -189,6 +190,7 @@
 					</div>
 
 					<div>
+						<!-- svelte-ignore a11y-label-has-associated-control -->
 						<label class="text-sm font-medium block mb-1">
 							{$t('adventures.arrival_timezone')}
 						</label>
@@ -366,8 +368,8 @@
 		</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"

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)'
 		};
 	}
 

frontend/src/locales/de.json

@@ -259,7 +259,9 @@
     "timezone": "Zeitzone",
     "no_visits": "Keine Besuche",
     "arrival_timezone": "Ankunftszeitzone",
-    "departure_timezone": "Abfahrtszeit"
+    "departure_timezone": "Abfahrtszeit",
+    "arrival_date": "Ankunftsdatum",
+    "departure_date": "Abflugdatum"
   },
   "home": {
     "desc_1": "Entdecken, planen und erkunden Sie mühelos",

frontend/src/locales/en.json

@@ -67,6 +67,8 @@
 		"no_visits": "No visits",
 		"departure_timezone": "Departure Timezone",
 		"arrival_timezone": "Arrival Timezone",
+		"departure_date": "Departure Date",
+		"arrival_date": "Arrival Date",
 		"no_image_found": "No image found",
 		"collection_link_error": "Error linking adventure to collection",
 		"adventure_delete_confirm": "Are you sure you want to delete this adventure? This action cannot be undone.",

frontend/src/locales/es.json

@@ -307,7 +307,9 @@
     "timezone": "Zona horaria",
     "no_visits": "No hay visitas",
     "arrival_timezone": "Zona horaria de llegada",
-    "departure_timezone": "Zona horaria de salida"
+    "departure_timezone": "Zona horaria de salida",
+    "arrival_date": "Fecha de llegada",
+    "departure_date": "Fecha de salida"
   },
   "worldtravel": {
     "all": "Todo",

frontend/src/locales/fr.json

@@ -259,7 +259,9 @@
     "timezone": "Fuseau horaire",
     "no_visits": "Pas de visites",
     "arrival_timezone": "Fuseau horaire d'arrivée",
-    "departure_timezone": "Fuseau horaire de départ"
+    "departure_timezone": "Fuseau horaire de départ",
+    "arrival_date": "Date d'arrivée",
+    "departure_date": "Date de départ"
   },
   "home": {
     "desc_1": "Découvrez, planifiez et explorez en toute simplicité",

frontend/src/locales/it.json

@@ -259,7 +259,9 @@
     "timezone": "Fuso orario",
     "no_visits": "Nessuna visita",
     "arrival_timezone": "Fuso orario di arrivo",
-    "departure_timezone": "Fuso orario di partenza"
+    "departure_timezone": "Fuso orario di partenza",
+    "arrival_date": "Data di arrivo",
+    "departure_date": "Data di partenza"
   },
   "home": {
     "desc_1": "Scopri, pianifica ed esplora con facilità",

frontend/src/locales/ko.json

@@ -259,7 +259,9 @@
     "timezone": "시간대",
     "no_visits": "방문 없음",
     "arrival_timezone": "도착 시간대",
-    "departure_timezone": "출발 시간대"
+    "departure_timezone": "출발 시간대",
+    "arrival_date": "도착 날짜",
+    "departure_date": "출발 날짜"
   },
   "auth": {
     "both_passwords_required": "두 암호 모두 필요합니다",

frontend/src/locales/nl.json

@@ -259,7 +259,9 @@
     "timezone": "Tijdzone",
     "no_visits": "Geen bezoeken",
     "arrival_timezone": "Aankomsttijdzone",
-    "departure_timezone": "Vertrektijdzone"
+    "departure_timezone": "Vertrektijdzone",
+    "arrival_date": "Aankomstdatum",
+    "departure_date": "Vertrekdatum"
   },
   "home": {
     "desc_1": "Ontdek, plan en verken met gemak",

frontend/src/locales/no.json

@@ -307,7 +307,9 @@
     "timezone": "Tidssone",
     "no_visits": "Ingen besøk",
     "arrival_timezone": "Ankomst tidssone",
-    "departure_timezone": "Avgangstidssone"
+    "departure_timezone": "Avgangstidssone",
+    "arrival_date": "Ankomstdato",
+    "departure_date": "Avgangsdato"
   },
   "worldtravel": {
     "country_list": "Liste over land",

frontend/src/locales/pl.json

@@ -307,7 +307,9 @@
     "timezone": "Strefa czasowa",
     "no_visits": "Brak wizyt",
     "arrival_timezone": "Strefa czasowa przyjazdu",
-    "departure_timezone": "Strefa czasowa odlotu"
+    "departure_timezone": "Strefa czasowa odlotu",
+    "arrival_date": "Data przyjazdu",
+    "departure_date": "Data wyjazdu"
   },
   "worldtravel": {
     "country_list": "Lista krajów",

frontend/src/locales/sv.json

@@ -259,7 +259,9 @@
     "timezone": "Tidszon",
     "no_visits": "Inga besök",
     "arrival_timezone": "Ankomsttidszon",
-    "departure_timezone": "Avgångstidszon"
+    "departure_timezone": "Avgångstidszon",
+    "arrival_date": "Ankomstdatum",
+    "departure_date": "Avgångsdatum"
   },
   "home": {
     "desc_1": "Upptäck, planera och utforska med lätthet",

frontend/src/locales/zh.json

@@ -307,7 +307,9 @@
     "timezone": "时区",
     "no_visits": "没有访问",
     "arrival_timezone": "到达时区",
-    "departure_timezone": "离开时区"
+    "departure_timezone": "离开时区",
+    "arrival_date": "到达日期",
+    "departure_date": "出发日期"
   },
   "auth": {
     "forgot_password": "忘记密码？",