diff --git a/client/src/config/reservationConfig.ts b/client/src/config/reservationConfig.ts
index 9bf9b01..cc566fe 100644
--- a/client/src/config/reservationConfig.ts
+++ b/client/src/config/reservationConfig.ts
@@ -1,14 +1,25 @@
 const configuredReservationHotelId = import.meta.env.VITE_RESERVATION_HOTEL_ID?.trim()
 
 export const reservationHotelId = configuredReservationHotelId || null
+export const reservationTimeZone = 'Asia/Bangkok'
 
 let reservationHotelIdProvider: (() => string | null | undefined) | null = null
+let reservationTimeZoneProvider: (() => string | null | undefined) | null = null
 
 export function setReservationHotelIdProvider(provider: (() => string | null | undefined) | null): void {
   reservationHotelIdProvider = provider
 }
 
+export function setReservationTimeZoneProvider(provider: (() => string | null | undefined) | null): void {
+  reservationTimeZoneProvider = provider
+}
+
 export function getReservationHotelId(): string | null {
   const providedHotelId = reservationHotelIdProvider?.()?.trim()
   return providedHotelId || reservationHotelId
 }
+
+export function getReservationTimeZone(): string {
+  const providedTimeZone = reservationTimeZoneProvider?.()?.trim()
+  return providedTimeZone || reservationTimeZone
+}
diff --git a/client/src/main.ts b/client/src/main.ts
index 84a5ef4..83e68d8 100644
--- a/client/src/main.ts
+++ b/client/src/main.ts
@@ -6,7 +6,10 @@ import { VueQueryPlugin } from '@tanstack/vue-query'
 import 'primeicons/primeicons.css'
 
 import App from './App.vue'
-import { setReservationHotelIdProvider } from './config/reservationConfig'
+import {
+  setReservationHotelIdProvider,
+  setReservationTimeZoneProvider,
+} from './config/reservationConfig'
 import { i18n } from './i18n'
 import { router } from './router'
 import { setUnauthorizedHandler } from './services/httpClient'
@@ -18,6 +21,7 @@ const pinia = createPinia()
 const authStore = useAuthStore(pinia)
 
 setReservationHotelIdProvider(() => authStore.selectedHotelId)
+setReservationTimeZoneProvider(() => authStore.selectedHotel?.time_zone)
 setUnauthorizedHandler(() => {
   const currentPath = router.currentRoute.value.fullPath
   authStore.clearAuth()
diff --git a/client/src/tests/reservationFormat.spec.ts b/client/src/tests/reservationFormat.spec.ts
new file mode 100644
index 0000000..f6b7429
--- /dev/null
+++ b/client/src/tests/reservationFormat.spec.ts
@@ -0,0 +1,45 @@
+import { afterEach, describe, expect, it } from 'vitest'
+
+import {
+  setReservationTimeZoneProvider,
+} from '@/config/reservationConfig'
+import {
+  formatReservationDateRange,
+  formatReservationDateTime,
+} from '@/utils/reservationFormat'
+
+describe('reservationFormat', () => {
+  afterEach(() => {
+    setReservationTimeZoneProvider(null)
+  })
+
+  it('formats UTC API timestamps in the default hotel time zone', () => {
+    expect(formatReservationDateTime('2026-07-09T05:56:56Z')).toBe('2026-07-09 12:56:56')
+  })
+
+  it('formats timestamps in the selected hotel time zone', () => {
+    setReservationTimeZoneProvider(() => 'Asia/Tokyo')
+
+    expect(formatReservationDateTime('2026-07-09T05:56:56Z')).toBe('2026-07-09 14:56:56')
+  })
+
+  it('honors offsets from source timestamps before converting to hotel time', () => {
+    expect(formatReservationDateTime('2026-07-08T09:18:00+08:00')).toBe('2026-07-08 08:18:00')
+  })
+
+  it('falls back to the default hotel time zone when the selected hotel timezone is invalid', () => {
+    setReservationTimeZoneProvider(() => 'Invalid/Timezone')
+
+    expect(formatReservationDateTime('2026-07-09T05:56:56Z')).toBe('2026-07-09 12:56:56')
+  })
+
+  it('falls back safely for empty or invalid timestamps', () => {
+    expect(formatReservationDateTime(null)).toBe('-')
+    expect(formatReservationDateTime(undefined)).toBe('-')
+    expect(formatReservationDateTime('not-a-date')).toBe('not-a-date')
+  })
+
+  it('keeps hotel business date ranges as local dates without timezone conversion', () => {
+    expect(formatReservationDateRange('2026-07-09', '2026-07-10')).toBe('2026-07-09 / 2026-07-10')
+  })
+})
diff --git a/client/src/utils/reservationFormat.ts b/client/src/utils/reservationFormat.ts
index 230d106..f962888 100644
--- a/client/src/utils/reservationFormat.ts
+++ b/client/src/utils/reservationFormat.ts
@@ -1,8 +1,14 @@
+import { getReservationTimeZone, reservationTimeZone } from '@/config/reservationConfig'
+
 export function formatReservationDateTime(value: string | null | undefined): string {
   if (!value) {
     return '-'
   }
-  return value.replace('T', ' ').replace(/\+.*$/, '')
+  const date = new Date(value)
+  if (Number.isNaN(date.getTime())) {
+    return value
+  }
+  return formatDateTimeInTimeZone(date, getReservationTimeZone())
 }
 
 export function formatReservationDateRange(arrivalDate: string, departureDate: string): string {
@@ -16,3 +22,26 @@ export function formatReservationCurrency(amount: number, currencyCode: string):
     maximumFractionDigits: 0,
   }).format(amount)
 }
+
+function formatDateTimeInTimeZone(date: Date, timeZone: string): string {
+  try {
+    return formatDateTimeParts(date, timeZone)
+  } catch {
+    return formatDateTimeParts(date, reservationTimeZone)
+  }
+}
+
+function formatDateTimeParts(date: Date, timeZone: string): string {
+  const parts = new Intl.DateTimeFormat('en-GB', {
+    timeZone,
+    year: 'numeric',
+    month: '2-digit',
+    day: '2-digit',
+    hour: '2-digit',
+    minute: '2-digit',
+    second: '2-digit',
+    hourCycle: 'h23',
+  }).formatToParts(date)
+  const valueByType = Object.fromEntries(parts.map((part) => [part.type, part.value]))
+  return `${valueByType.year}-${valueByType.month}-${valueByType.day} ${valueByType.hour}:${valueByType.minute}:${valueByType.second}`
+}
diff --git a/client/src/views/debug/DebugEmlSuperAgentRunView.vue b/client/src/views/debug/DebugEmlSuperAgentRunView.vue
index 2d32d37..3000747 100644
--- a/client/src/views/debug/DebugEmlSuperAgentRunView.vue
+++ b/client/src/views/debug/DebugEmlSuperAgentRunView.vue
@@ -217,23 +217,33 @@
               <dl class="debug-eml-trace-fields">
                 <div v-if="trace.tool_name">
                   <dt>{{ t('debugEml.traceToolName') }}</dt>
-                  <dd class="th-code">{{ trace.tool_name }}</dd>
+                  <dd class="th-code">
+                    {{ trace.tool_name }}
+                  </dd>
                 </div>
                 <div v-if="trace.input_summary">
                   <dt>{{ t('debugEml.traceInputSummary') }}</dt>
-                  <dd class="th-code">{{ trace.input_summary }}</dd>
+                  <dd class="th-code">
+                    {{ trace.input_summary }}
+                  </dd>
                 </div>
                 <div v-if="trace.output_summary">
                   <dt>{{ t('debugEml.traceOutputSummary') }}</dt>
-                  <dd class="th-code">{{ trace.output_summary }}</dd>
+                  <dd class="th-code">
+                    {{ trace.output_summary }}
+                  </dd>
                 </div>
                 <div v-if="trace.status">
                   <dt>{{ t('debugEml.traceStatus') }}</dt>
-                  <dd class="th-code">{{ trace.status }}</dd>
+                  <dd class="th-code">
+                    {{ trace.status }}
+                  </dd>
                 </div>
                 <div v-if="trace.ts">
                   <dt>{{ t('debugEml.traceTime') }}</dt>
-                  <dd class="th-code">{{ trace.ts }}</dd>
+                  <dd class="th-code">
+                    {{ formatReservationDateTime(trace.ts) }}
+                  </dd>
                 </div>
               </dl>
             </li>
@@ -437,6 +447,7 @@ import type {
   DebugEmlSuperAgentRunResult,
   DebugEmlSuperAgentTraceEvent,
 } from '@/types/debugEml'
+import { formatReservationDateTime } from '@/utils/reservationFormat'
 
 type DebugEmlStatus = 'idle' | 'uploading' | 'succeeded' | 'failed'