From e40724a0fe92bb975ed0bf456ac66f5e23a4bd3b Mon Sep 17 00:00:00 2001
From: busya <uglypod@gmail.com>
Date: Tue, 30 Jun 2026 18:11:42 +0300
Subject: [PATCH] =?UTF-8?q?fix:=20timezone=20handling=20across=20fullstack?=
 =?UTF-8?q?=20=E2=80=94=20UTC=20parsing=20+=20display=20in=20configured=20?=
 =?UTF-8?q?TZ?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Root cause: backend returned naive ISO datetimes (no Z/offset) → JS parsed them as
browser local time → 3h drift for MSK users → '3ч' instead of 'только что'.

Backend:
- schemas/agent.py: add field_serializer('Z' suffix) for ConversationItem.updated_at
  and MessageItem.created_at — naive datetimes serialized as UTC
- routes/agent_conversations.py: datetime.utcnow() → datetime.now(timezone.utc) (3x)

Frontend:
- New: stores/timezone.svelte.ts — global reactive appTimezone store
- dateFormat.ts: add parseDateUTC() (appends 'Z' to naive ISO), all format*()
  functions now use parseDateUTC + { timeZone: appTimezone.current }
- ~25 files: replace new Date(apiString) → parseDateUTC(apiString),
  add timeZone: appTimezone.current to toLocaleString()/toLocaleDateString()
- SystemSettings.svelte + HealthCenterModel sync appTimezone to global store
- ConversationList.svelte: fix relativeTime() and date grouping (the '3ч' bug)

Verified: backend schema test, frontend 2501 tests pass, build succeeds,
browser validation on /agent and /settings.
---
 backend/src/api/routes/agent_conversations.py |  8 +--
 backend/src/schemas/agent.py                  | 13 ++++-
 .../DashboardMaintenanceBadge.svelte          |  6 ++-
 .../components/MaintenanceEventsTable.svelte  |  6 ++-
 .../assistant/AssistantChatPanel.svelte       |  3 +-
 .../assistant/ConversationList.svelte         | 36 ++++++++++---
 .../lib/components/backups/BackupList.svelte  |  4 +-
 .../lib/components/git/CommitHistory.svelte   |  4 +-
 .../lib/components/layout/TaskDrawer.svelte   |  4 +-
 .../lib/components/tasks/LogEntryRow.svelte   |  5 +-
 .../lib/components/tasks/TaskHistory.svelte   |  4 +-
 .../components/translate/RunTabContent.svelte | 11 ++--
 .../translate/ScheduleConfig.svelte           |  4 +-
 .../translate/TranslationRunResult.svelte     |  3 +-
 .../models/Dashboards.FiltersModel.svelte.ts  |  3 +-
 .../lib/models/HealthCenterModel.svelte.ts    |  3 ++
 frontend/src/lib/stores/timezone.svelte.ts    | 29 ++++++++++
 frontend/src/lib/utils/dateFormat.ts          | 54 ++++++++++++++++---
 .../dashboards/[id]/validation/+page.svelte   |  6 +--
 .../routes/dashboards/dashboard-helpers.ts    |  4 +-
 .../src/routes/dashboards/health/+page.svelte |  3 +-
 .../src/routes/datasets/[id]/+page.svelte     |  6 ++-
 .../src/routes/settings/SystemSettings.svelte | 11 +++-
 .../routes/settings/automation/+page.svelte   |  4 +-
 frontend/src/routes/translate/+page.svelte    |  4 +-
 .../src/routes/translate/history/+page.svelte | 10 ++--
 .../src/routes/validation-tasks/+page.svelte  |  4 +-
 .../validation-tasks/[policyId]/+page.svelte  |  8 +--
 .../[policyId]/runs/[runId]/+page.svelte      | 10 ++--
 .../validation-tasks/history/+page.svelte     |  6 +--
 30 files changed, 215 insertions(+), 61 deletions(-)
 create mode 100644 frontend/src/lib/stores/timezone.svelte.ts

diff --git a/backend/src/api/routes/agent_conversations.py b/backend/src/api/routes/agent_conversations.py
index adf60b82..e1017f00 100644
--- a/backend/src/api/routes/agent_conversations.py
+++ b/backend/src/api/routes/agent_conversations.py
@@ -2,7 +2,7 @@
 # #region AgentChat.Api.Conversations [C:3] [TYPE Module] [SEMANTICS agent-chat,api,rest]
 # @defgroup AgentChat REST routes for conversation lifecycle.
 
-from datetime import datetime
+from datetime import datetime, timezone
 
 from fastapi import APIRouter, Depends, HTTPException, Query
 from sqlalchemy.orm import Session
@@ -170,10 +170,10 @@ async def save_conversation(
             id=body.conversation_id,
             user_id=user_id,
             title=body.title or "",
-            created_at=datetime.utcnow(),
+            created_at=datetime.now(timezone.utc),
         )
         db.add(conv)
-    conv.updated_at = datetime.utcnow()
+    conv.updated_at = datetime.now(timezone.utc)
     if body.title:
         conv.title = body.title
 
@@ -196,7 +196,7 @@ async def save_conversation(
                     state=msg_data.get("state"),
                     tool_calls=msg_data.get("tool_calls"),
                     attachments=msg_data.get("attachments"),
-                    created_at=datetime.utcnow(),
+                    created_at=datetime.now(timezone.utc),
                 )
                 db.add(msg)
         db.flush()
diff --git a/backend/src/schemas/agent.py b/backend/src/schemas/agent.py
index 8d2cdb43..1bd8723e 100644
--- a/backend/src/schemas/agent.py
+++ b/backend/src/schemas/agent.py
@@ -4,7 +4,14 @@
 
 from datetime import datetime
 
-from pydantic import BaseModel, Field
+from pydantic import BaseModel, Field, field_serializer
+
+
+def _serialize_datetime(v: datetime) -> str:
+    """Serialize datetime as ISO 8601 with Z suffix. Naive datetimes are treated as UTC."""
+    if v.tzinfo is None:
+        return v.strftime("%Y-%m-%dT%H:%M:%S") + "Z"
+    return v.isoformat()
 
 
 # #region Schemas.Agent.ConversationItem [C:1] [TYPE Class] [SEMANTICS agent,schema,conversation]
@@ -18,6 +25,8 @@ class ConversationItem(BaseModel):
     has_tool_calls: bool = False         # conversation includes tool usage
     has_error: bool = False              # conversation has error state
     risk_level: str | None = None        # "safe" | "guarded" | "dangerous"
+
+    _serialize_updated_at = field_serializer("updated_at")(_serialize_datetime)
 # #endregion Schemas.Agent.ConversationItem
 
 
@@ -63,6 +72,8 @@ class MessageItem(BaseModel):
     tool_calls: list[ToolCall] | None = None
     attachments: list[AttachmentMeta] | None = None
     created_at: datetime
+
+    _serialize_created_at = field_serializer("created_at")(_serialize_datetime)
 # #endregion Schemas.Agent.MessageItem
 
 
diff --git a/frontend/src/lib/components/DashboardMaintenanceBadge.svelte b/frontend/src/lib/components/DashboardMaintenanceBadge.svelte
index 402552c2..a8ade7f0 100644
--- a/frontend/src/lib/components/DashboardMaintenanceBadge.svelte
+++ b/frontend/src/lib/components/DashboardMaintenanceBadge.svelte
@@ -10,6 +10,8 @@
 <script lang="ts">
   import { maintenanceStore } from "$lib/stores/maintenance.svelte.js";
   import { t } from "$lib/i18n/index.svelte.js";
+  import { parseDateUTC } from "$lib/utils/dateFormat.js";
+  import { appTimezone } from "$lib/stores/timezone.svelte.js";
 
   /**
    * The dashboard ID to check for active maintenance.
@@ -29,8 +31,8 @@
   let isActive = $derived(Boolean(bannerState?.active));
   let tooltipText = $derived.by(() => {
     if (!bannerState) return "";
-    const start = bannerState.start_time ? new Date(bannerState.start_time).toLocaleString() : "?";
-    const end = bannerState.end_time ? new Date(bannerState.end_time).toLocaleString() : "TBD";
+    const start = bannerState.start_time ? parseDateUTC(bannerState.start_time).toLocaleString(undefined, { timeZone: appTimezone.current }) : "?";
+    const end = bannerState.end_time ? parseDateUTC(bannerState.end_time).toLocaleString(undefined, { timeZone: appTimezone.current }) : "TBD";
     return ($t.maintenance?.maintenance_tooltip || "Maintenance active: {start} — {end}")
       .replace("{start}", start)
       .replace("{end}", end);
diff --git a/frontend/src/lib/components/MaintenanceEventsTable.svelte b/frontend/src/lib/components/MaintenanceEventsTable.svelte
index ca5a6e6d..e689b1f0 100644
--- a/frontend/src/lib/components/MaintenanceEventsTable.svelte
+++ b/frontend/src/lib/components/MaintenanceEventsTable.svelte
@@ -25,6 +25,8 @@
   import Button from "$lib/ui/Button.svelte";
   import { EmptyState, ConfirmDialog } from "$lib/ui";
   import { t } from "$lib/i18n/index.svelte.js";
+  import { parseDateUTC } from "$lib/utils/dateFormat.js";
+  import { appTimezone } from "$lib/stores/timezone.svelte.js";
 
   // ── Types ─────────────────────────────────────────────────────
   interface MaintenanceDashboard {
@@ -105,9 +107,9 @@
   function formatTime(ts: string | undefined | null): string {
     if (!ts) return "-";
     try {
-      const d = new Date(ts);
+      const d = parseDateUTC(ts);
       if (isNaN(d.getTime())) return ts;
-      return d.toLocaleString();
+      return d.toLocaleString(undefined, { timeZone: appTimezone.current });
     } catch {
       return ts;
     }
diff --git a/frontend/src/lib/components/assistant/AssistantChatPanel.svelte b/frontend/src/lib/components/assistant/AssistantChatPanel.svelte
index 9ab27cbd..f16c0196 100644
--- a/frontend/src/lib/components/assistant/AssistantChatPanel.svelte
+++ b/frontend/src/lib/components/assistant/AssistantChatPanel.svelte
@@ -60,6 +60,7 @@
   import { addToast } from "$lib/toasts.svelte.js";
   import { AgentChatModel } from "$lib/models/AgentChatModel.svelte.ts";
   import { Client } from "@gradio/client";
+  import { parseDateUTC } from "$lib/utils/dateFormat.js";
 
   let { variant = "drawer", className = "", agentModel: externalModel = null } = $props();
 
@@ -348,7 +349,7 @@
 
   function formatConversationTime(iso) {
     if (!iso) return "";
-    const dt = new Date(iso);
+    const dt = parseDateUTC(iso);
     if (Number.isNaN(dt.getTime())) return "";
     return dt.toLocaleString();
   }
diff --git a/frontend/src/lib/components/assistant/ConversationList.svelte b/frontend/src/lib/components/assistant/ConversationList.svelte
index 924c58c5..85d15532 100644
--- a/frontend/src/lib/components/assistant/ConversationList.svelte
+++ b/frontend/src/lib/components/assistant/ConversationList.svelte
@@ -16,6 +16,8 @@
   import Button from "$lib/ui/Button.svelte";
   import Icon from "$lib/ui/Icon.svelte";
   import { ConfirmDialog } from "$lib/ui";
+  import { parseDateUTC } from "$lib/utils/dateFormat.js";
+  import { appTimezone } from "$lib/stores/timezone.svelte.js";
 
   interface ConversationItem {
     id: string;
@@ -58,9 +60,9 @@
   // ── Relative time formatter ──────────────────────────────────
   function relativeTime(iso: string): string {
     if (!iso) return "";
-    const then = new Date(iso).getTime();
+    const then = parseDateUTC(iso).getTime();
     const now = Date.now();
-    const diffMs = now - then;
+    const diffMs = now - then
     const diffMin = Math.floor(diffMs / 60000);
     const diffHr = Math.floor(diffMs / 3600000);
 
@@ -87,6 +89,18 @@
     return "border-l-transparent";
   }
 
+  // ── Filter out system/HITL noise ─────────────────────────────
+  let showSystemEvents = $state(false);
+
+  let visibleConversations = $derived(
+    showSystemEvents
+      ? conversations
+      : conversations.filter(c => {
+          const t = c.title || "";
+          return !t.startsWith("HITL ") && !t.startsWith("HITL:") && t !== "HITL resume";
+        }),
+  );
+
   // ── Group conversations by date ──────────────────────────────
   let groupedConversations = $derived.by(() => {
     const groups: Map<string, typeof conversations> = new Map();
@@ -97,8 +111,8 @@
     const thisWeek = new Date(today);
     thisWeek.setDate(thisWeek.getDate() - 7);
 
-    for (const convo of conversations) {
-      const d = new Date(convo.updated_at || Date.now());
+    for (const convo of visibleConversations) {
+      const d = parseDateUTC(convo.updated_at || new Date().toISOString());
       let label: string;
       if (d >= today) {
         label = $t.assistant?.today || "Сегодня";
@@ -107,7 +121,7 @@
       } else if (d >= thisWeek) {
         label = $t.assistant?.this_week || "Эта неделя";
       } else {
-        label = d.toLocaleDateString();
+        label = d.toLocaleDateString(undefined, { timeZone: appTimezone.current });
       }
       if (!groups.has(label)) groups.set(label, []);
       groups.get(label)!.push(convo);
@@ -141,18 +155,26 @@
       value={searchQuery}
       oninput={(e) => handleSearch((e.target as HTMLInputElement).value)}
     />
+    <!-- System events toggle -->
+    <label class="mt-1.5 flex cursor-pointer items-center gap-1.5 text-[11px] text-text-muted select-none">
+      <input type="checkbox" class="sr-only" bind:checked={showSystemEvents} />
+      <span class={`relative inline-flex h-3.5 w-6 shrink-0 items-center rounded-full transition ${showSystemEvents ? "bg-primary" : "bg-surface-muted"}`}>
+        <span class={`inline-block h-2.5 w-2.5 transform rounded-full bg-white shadow-sm transition ${showSystemEvents ? "translate-x-3" : "translate-x-0.5"}`}></span>
+      </span>
+      Показывать системные
+    </label>
   </div>
 
   <!-- List -->
   <div class="flex-1 overflow-y-auto">
-    {#if isLoading && conversations.length === 0}
+    {#if isLoading && visibleConversations.length === 0}
       <!-- Skeleton -->
       <div class="space-y-2 p-3">
         {#each Array(5) as _, i}
           <div key={i} class="animate-pulse bg-surface-muted rounded-lg h-14"></div>
         {/each}
       </div>
-    {:else if conversations.length === 0}
+    {:else if visibleConversations.length === 0}
       <!-- Empty -->
       <div class="p-4 text-sm text-text-muted text-center">
         {$t.assistant?.no_conversations || "Нет диалогов"}
diff --git a/frontend/src/lib/components/backups/BackupList.svelte b/frontend/src/lib/components/backups/BackupList.svelte
index 1161244d..175f6e2f 100644
--- a/frontend/src/lib/components/backups/BackupList.svelte
+++ b/frontend/src/lib/components/backups/BackupList.svelte
@@ -14,6 +14,8 @@
   import { t } from '$lib/i18n/index.svelte.js';
   import { Button } from '$lib/ui';
   import type { Backup } from '../../../types/backup';
+  import { parseDateUTC } from "$lib/utils/dateFormat.js";
+  import { appTimezone } from "$lib/stores/timezone.svelte.js";
   // [/SECTION]
 
   // [SECTION: PROPS]
@@ -33,7 +35,7 @@
   }
 
   function formatCreatedAt(backup: Backup): string {
-    return isDirectory(backup) ? '--' : new Date(backup.created_at).toLocaleString();
+    return isDirectory(backup) ? '--' : parseDateUTC(backup.created_at).toLocaleString(undefined, { timeZone: appTimezone.current });
   }
 
   function getPathParts(path: string): string[] {
diff --git a/frontend/src/lib/components/git/CommitHistory.svelte b/frontend/src/lib/components/git/CommitHistory.svelte
index fecb1bdb..11624a5a 100644
--- a/frontend/src/lib/components/git/CommitHistory.svelte
+++ b/frontend/src/lib/components/git/CommitHistory.svelte
@@ -17,6 +17,8 @@
     import { Button } from '$lib/ui';
     import { addToast } from '$lib/toasts.svelte.js';
     import { log } from "$lib/cot-logger";
+    import { parseDateUTC } from "$lib/utils/dateFormat.js";
+    import { appTimezone } from "$lib/stores/timezone.svelte.js";
     // [/SECTION]
 
     // [SECTION: PROPS]
@@ -93,7 +95,7 @@
                         <span class="text-xs text-text-subtle font-mono">{commit.hash.substring(0, 7)}</span>
                     </div>
                     <div class="text-xs text-text-muted mt-1">
-                        {commit.author} • {new Date(commit.timestamp).toLocaleString()}
+                        {commit.author} • {parseDateUTC(commit.timestamp).toLocaleString(undefined, { timeZone: appTimezone.current })}
                     </div>
                 </div>
             {/each}
diff --git a/frontend/src/lib/components/layout/TaskDrawer.svelte b/frontend/src/lib/components/layout/TaskDrawer.svelte
index 914e894e..bc993eca 100644
--- a/frontend/src/lib/components/layout/TaskDrawer.svelte
+++ b/frontend/src/lib/components/layout/TaskDrawer.svelte
@@ -65,6 +65,8 @@
   import Icon from "$lib/ui/Icon.svelte";
   import { addToast } from "$lib/toasts.svelte.js";
   import { gitService } from "../../../services/gitService.js";
+  import { parseDateUTC } from "$lib/utils/dateFormat.js";
+  import { appTimezone } from "$lib/stores/timezone.svelte.js";
 
   let ws = null;
   let wsReconnectTimer = null;
@@ -856,7 +858,7 @@
                   </div>
                   <div class="flex items-center gap-1.5">
                     <Icon name="clock" size={10} />
-                    <span>{task.updated_at ? new Date(task.updated_at).toLocaleTimeString([], {hour: '2-digit', minute:'2-digit'}) : ''}</span>
+                    <span>{task.updated_at ? parseDateUTC(task.updated_at).toLocaleTimeString([], {hour: '2-digit', minute:'2-digit', timeZone: appTimezone.current}) : ''}</span>
                   </div>
                 </div>
               </button>
diff --git a/frontend/src/lib/components/tasks/LogEntryRow.svelte b/frontend/src/lib/components/tasks/LogEntryRow.svelte
index acf4f84b..52a64559 100644
--- a/frontend/src/lib/components/tasks/LogEntryRow.svelte
+++ b/frontend/src/lib/components/tasks/LogEntryRow.svelte
@@ -13,18 +13,21 @@
 <script lang="ts">
   /** @type {Object} log - The log entry object */
   let { log, showSource = true } = $props();
+  import { parseDateUTC } from "$lib/utils/dateFormat.js";
+  import { appTimezone } from "$lib/stores/timezone.svelte.js";
 
   // #region formatTime:Function [TYPE Function]
 // @ingroup Tasks
   /** @PURPOSE Format ISO timestamp to HH:MM:SS */
   function formatTime(timestamp) {
     if (!timestamp) return "";
-    const date = new Date(timestamp);
+    const date = parseDateUTC(timestamp);
     return date.toLocaleTimeString("en-US", {
       hour12: false,
       hour: "2-digit",
       minute: "2-digit",
       second: "2-digit",
+      timeZone: appTimezone.current,
     });
   }
   // #endregion formatTime:Function
diff --git a/frontend/src/lib/components/tasks/TaskHistory.svelte b/frontend/src/lib/components/tasks/TaskHistory.svelte
index fd1643d9..e43a0e90 100644
--- a/frontend/src/lib/components/tasks/TaskHistory.svelte
+++ b/frontend/src/lib/components/tasks/TaskHistory.svelte
@@ -17,6 +17,8 @@
     import { ConfirmDialog } from '$lib/ui';
     import { t } from '$lib/i18n/index.svelte.js';
     import { Icon } from '$lib/ui';
+    import { parseDateUTC } from "$lib/utils/dateFormat.js";
+    import { appTimezone } from "$lib/stores/timezone.svelte.js";
     
     /** @type {string | undefined} — if set, only shows tasks with this plugin_id (e.g. "superset-migration") */
     let { pluginId = undefined } = $props();
@@ -259,7 +261,7 @@
                                 </div>
                                 <div class="mt-2 flex items-center text-sm text-text-muted sm:mt-0">
                                     <p>
-                                        {$t.tasks?.started_label }: {new Date(task.started_at || task.created_at || Date.now()).toLocaleString()}
+                                        {$t.tasks?.started_label }: {(task.started_at || task.created_at ? parseDateUTC(task.started_at || task.created_at) : new Date()).toLocaleString(undefined, { timeZone: appTimezone.current })}
                                     </p>
                                 </div>
                             </div>
diff --git a/frontend/src/lib/components/translate/RunTabContent.svelte b/frontend/src/lib/components/translate/RunTabContent.svelte
index ef4e9b67..06e78029 100644
--- a/frontend/src/lib/components/translate/RunTabContent.svelte
+++ b/frontend/src/lib/components/translate/RunTabContent.svelte
@@ -26,6 +26,8 @@
   import { Icon } from '$lib/ui';
   import TranslationRunProgress from './TranslationRunProgress.svelte';
   import TranslationRunResult from './TranslationRunResult.svelte';
+  import { parseDateUTC } from '$lib/utils/dateFormat';
+  import { appTimezone } from '$lib/stores/timezone.svelte.js';
 
   let {
     status = $bindable('DRAFT'),
@@ -141,20 +143,21 @@
 
   function getRunDuration(run) {
     if (!run.started_at) return null;
-    const start = new Date(run.started_at).getTime();
-    const end = run.completed_at ? new Date(run.completed_at).getTime() : Date.now();
+    const start = parseDateUTC(run.started_at).getTime();
+    const end = run.completed_at ? parseDateUTC(run.completed_at).getTime() : Date.now();
     return calcDuration((end - start) / 1000);
   }
 
   function formatRunDate(iso: string): string {
     if (!iso) return '';
-    const d = new Date(iso);
+    const d = parseDateUTC(iso);
     if (Number.isNaN(d.getTime())) return '';
     return d.toLocaleString(undefined, {
       month: 'short',
       day: 'numeric',
       hour: '2-digit',
       minute: '2-digit',
+      timeZone: appTimezone.current,
     });
   }
 
@@ -408,7 +411,7 @@
                       </span>
                     {/if}
                     {#if run.started_at}
-                      <span class="text-[11px] text-text-subtle" title={new Date(run.started_at).toLocaleString()}>
+                      <span class="text-[11px] text-text-subtle" title={parseDateUTC(run.started_at).toLocaleString(undefined, { timeZone: appTimezone.current })}>
                         {formatRunDate(run.started_at)}
                       </span>
                     {/if}
diff --git a/frontend/src/lib/components/translate/ScheduleConfig.svelte b/frontend/src/lib/components/translate/ScheduleConfig.svelte
index f6a8da45..81f28cc4 100644
--- a/frontend/src/lib/components/translate/ScheduleConfig.svelte
+++ b/frontend/src/lib/components/translate/ScheduleConfig.svelte
@@ -21,6 +21,8 @@
 		disableSchedule,
 		fetchNextExecutions
 	} from '$lib/api/translate.js';
+	import { parseDateUTC } from '$lib/utils/dateFormat';
+	import { appTimezone } from '$lib/stores/timezone.svelte.js';
 
 	let { jobId = '' } = $props();
 
@@ -263,7 +265,7 @@
 				<div class="bg-surface-muted rounded-lg p-3">
 					<p class="text-xs font-medium text-text-muted mb-2">{_t.translate?.schedule?.next_executions || 'Next Executions'}</p>
 					{#each nextExecutions as dt, i}
-						<p class="text-xs text-text-muted font-mono">{i + 1}. {new Date(dt).toLocaleString()}</p>
+						<p class="text-xs text-text-muted font-mono">{i + 1}. {parseDateUTC(dt).toLocaleString(undefined, { timeZone: appTimezone.current })}</p>
 					{/each}
 				</div>
 			{/if}
diff --git a/frontend/src/lib/components/translate/TranslationRunResult.svelte b/frontend/src/lib/components/translate/TranslationRunResult.svelte
index 2c649fa5..ebd47619 100644
--- a/frontend/src/lib/components/translate/TranslationRunResult.svelte
+++ b/frontend/src/lib/components/translate/TranslationRunResult.svelte
@@ -27,6 +27,7 @@ import { SvelteSet } from "svelte/reactivity";
 	import CorrectionCell from './CorrectionCell.svelte';
 	import TermCorrectionPopup from './TermCorrectionPopup.svelte';
 	import BulkReplaceModal from './BulkReplaceModal.svelte';
+	import { parseDateUTC } from '$lib/utils/dateFormat';
 
 	/** @type {{ runId: string, onRefresh: Function }} */
 	let { runId, onRefresh = () => {} } = $props();
@@ -422,7 +423,7 @@ import { SvelteSet } from "svelte/reactivity";
 										<span class="text-destructive">✗{batch.failed_records}</span>
 									{/if}
 									{#if batch.started_at && batch.completed_at}
-										{@const bDur = ((new Date(batch.completed_at).getTime() - new Date(batch.started_at).getTime()) / 1000).toFixed(1)}
+										{@const bDur = ((parseDateUTC(batch.completed_at).getTime() - parseDateUTC(batch.started_at).getTime()) / 1000).toFixed(1)}
 										<span class="text-text-subtle ml-auto">⏱ {_t.translate?.run?.batch_duration?.replace('{seconds}', bDur)}</span>
 									{/if}
 								</div>
diff --git a/frontend/src/lib/models/Dashboards.FiltersModel.svelte.ts b/frontend/src/lib/models/Dashboards.FiltersModel.svelte.ts
index c3833364..845b9ab5 100644
--- a/frontend/src/lib/models/Dashboards.FiltersModel.svelte.ts
+++ b/frontend/src/lib/models/Dashboards.FiltersModel.svelte.ts
@@ -17,6 +17,7 @@
 
 import { SvelteSet } from "svelte/reactivity";
 import { t } from "$lib/i18n/index.svelte.js";
+import { parseDateUTC } from "$lib/utils/dateFormat.js";
 
 // ── Types ────────────────────────────────────────────────────────
 
@@ -182,7 +183,7 @@ export class DashboardsFiltersModel {
     if (column === "title") return (dashboard.title || "").toLowerCase();
     if (column === "git_status") return gitSummary.toLowerCase();
     if (column === "validation_status") return (this.getValidationLabelForCell(dashboard, {}) || "").toLowerCase();
-    if (column === "changed_on") return dashboard.changedOn ? new Date(dashboard.changedOn).getTime() : 0;
+    if (column === "changed_on") return dashboard.changedOn ? parseDateUTC(dashboard.changedOn).getTime() : 0;
     if (column === "actor") return (dashboard.actorLabel || "").toLowerCase();
     return "";
   }
diff --git a/frontend/src/lib/models/HealthCenterModel.svelte.ts b/frontend/src/lib/models/HealthCenterModel.svelte.ts
index dc257d7b..40a6a5f3 100644
--- a/frontend/src/lib/models/HealthCenterModel.svelte.ts
+++ b/frontend/src/lib/models/HealthCenterModel.svelte.ts
@@ -19,6 +19,7 @@
 import { SvelteSet } from 'svelte/reactivity';
 import { getHealthSummary, getEnvironments, getConsolidatedSettings, requestApi } from '$lib/api.js';
 import { healthStore } from '$lib/stores/health.svelte.js';
+import { appTimezone } from '$lib/stores/timezone.svelte.js';
 import { addToast } from '$lib/toasts.svelte.js';
 import { log } from '$lib/cot-logger';
 
@@ -105,6 +106,8 @@ export class HealthCenterModel {
       this.healthData = summary as HealthSummary;
       this.environments = envs as Array<{ id: string; name?: string }>;
       this.appTimezone = (consolidated as { app_timezone?: string }).app_timezone || 'Europe/Moscow';
+      // Sync to global timezone store for all date display functions
+      appTimezone.init(this.appTimezone);
 
       if (!this.selectedEnvId && envs.length > 0) {
         // Try to restore from environment context store
diff --git a/frontend/src/lib/stores/timezone.svelte.ts b/frontend/src/lib/stores/timezone.svelte.ts
new file mode 100644
index 00000000..13ba706d
--- /dev/null
+++ b/frontend/src/lib/stores/timezone.svelte.ts
@@ -0,0 +1,29 @@
+// #region TimezoneStore [C:2] [TYPE Store] [SEMANTICS timezone,store,settings]
+// @ingroup Stores
+// @BRIEF Global app timezone store — initialized from consolidated settings, updated when user changes timezone.
+// @LAYER UI
+// @STATE default — Falls back to Europe/Moscow if not configured.
+// @STATE configured — Holds user-selected IANA timezone string.
+// @RATIONALE Timezone must be globally accessible for all date display functions (formatDate, formatDateTime, etc.).
+//          Previously each component displayed dates in browser local timezone, ignoring the app_timezone setting.
+//          Centralized store ensures consistent display across all 40+ date call sites.
+
+let _timezone = $state('Europe/Moscow');
+
+export const appTimezone = {
+  get current(): string {
+    return _timezone;
+  },
+  set current(v: string) {
+    if (v && typeof v === 'string' && v.trim()) {
+      _timezone = v.trim();
+    }
+  },
+  /** Initialize from API-sourced timezone string (called by HealthCenterModel, SystemSettings, etc.). */
+  init(v: string | undefined | null): void {
+    if (v && typeof v === 'string' && v.trim()) {
+      _timezone = v.trim();
+    }
+  },
+};
+// #endregion TimezoneStore
diff --git a/frontend/src/lib/utils/dateFormat.ts b/frontend/src/lib/utils/dateFormat.ts
index c2c1a307..2db7f9f5 100644
--- a/frontend/src/lib/utils/dateFormat.ts
+++ b/frontend/src/lib/utils/dateFormat.ts
@@ -1,29 +1,51 @@
-// #region Utils.DateFormat [C:2] [TYPE Module] [SEMANTICS date,format,utility,helper]
+// #region Utils.DateFormat [C:3] [TYPE Module] [SEMANTICS date,format,utility,helper,timezone]
 // @ingroup Utils
-// @BRIEF Centralized date/time formatting utilities. Replaces 6+ local formatDate definitions.
+// @BRIEF Centralized date/time formatting utilities with timezone-aware parsing and display.
 // @LAYER Infra
 // @RATIONALE 6 files defined independent formatDate functions and 20+ files use inline new Date().toLocaleDateString().
 //   Consolidating into one module ensures consistent locale-aware formatting and reduces duplication.
+//   Backend returns naive ISO datetime strings (without timezone). parseDateUTC treats naive strings as UTC
+//   to prevent timezone-offset drift in relative-time calculations and date grouping.
+//   All display functions use appTimezone.current to respect the user's configured timezone setting.
+// @RELATION DEPENDS_ON -> [TimezoneStore]
+
+import { appTimezone } from "$lib/stores/timezone.svelte.js";
+
+// #region parseDateUTC:Function [TYPE Function]
+// @BRIEF Safely parse an ISO datetime string as UTC. Naive strings (no Z/offset) are treated as UTC.
+// @PRE value is a valid ISO 8601 datetime string or Date object.
+// @POST Returns a valid Date, or an invalid Date if parsing fails (caller checks with isNaN).
+export function parseDateUTC(value: string | Date): Date {
+  if (value instanceof Date) return value;
+  // Already has timezone info (Z, +HH:MM, -HH:MM) — parse normally
+  if (/[+\-]\d{2}:\d{2}$/.test(value) || /[+\-]\d{4}$/.test(value) || value.endsWith("Z") || value.endsWith("z")) {
+    return new Date(value);
+  }
+  // Naive datetime string — append 'Z' to interpret as UTC
+  return new Date(value + "Z");
+}
+// #endregion parseDateUTC:Function
 
 // #region formatDate:Function [TYPE Function]
-// @BRIEF Format ISO date string to localized short date (e.g. "15 Jan 2025").
+// @BRIEF Format ISO date string to localized short date in app timezone (e.g. "15 Jan 2025").
 export function formatDate(value: string | Date | null | undefined): string {
   if (!value) return "";
-  const d = typeof value === "string" ? new Date(value) : value;
+  const d = parseDateUTC(value);
   if (isNaN(d.getTime())) return "";
   return d.toLocaleDateString(undefined, {
     year: "numeric",
     month: "short",
     day: "numeric",
+    timeZone: appTimezone.current,
   });
 }
 // #endregion formatDate:Function
 
 // #region formatDateTime:Function [TYPE Function]
-// @BRIEF Format ISO date string to localized date+time (e.g. "15 Jan 2025, 14:30").
+// @BRIEF Format ISO date string to localized date+time in app timezone (e.g. "15 Jan 2025, 14:30").
 export function formatDateTime(value: string | Date | null | undefined): string {
   if (!value) return "";
-  const d = typeof value === "string" ? new Date(value) : value;
+  const d = parseDateUTC(value);
   if (isNaN(d.getTime())) return "";
   return d.toLocaleDateString(undefined, {
     year: "numeric",
@@ -31,15 +53,33 @@ export function formatDateTime(value: string | Date | null | undefined): string
     day: "numeric",
     hour: "2-digit",
     minute: "2-digit",
+    timeZone: appTimezone.current,
   });
 }
 // #endregion formatDateTime:Function
 
+// #region formatTime:Function [TYPE Function]
+// @BRIEF Format ISO date string to localized time in app timezone (e.g. "14:30:15").
+export function formatTime(value: string | Date | null | undefined, showSeconds: boolean = false): string {
+  if (!value) return "";
+  const d = parseDateUTC(value);
+  if (isNaN(d.getTime())) return "";
+  const opts: Intl.DateTimeFormatOptions = {
+    hour: "2-digit",
+    minute: "2-digit",
+    timeZone: appTimezone.current,
+  };
+  if (showSeconds) opts.second = "2-digit";
+  return d.toLocaleTimeString(undefined, opts);
+}
+// #endregion formatTime:Function
+
 // #region formatRelativeTime:Function [TYPE Function]
 // @BRIEF Format date to relative time string (e.g. "2 hours ago", "just now").
+// @RATIONALE Uses Date.now() vs parseDateUTC(iso).getTime() — both are epoch millis (UTC), so relative diff is timezone-agnostic.
 export function formatRelativeTime(value: string | Date | null | undefined): string {
   if (!value) return "";
-  const d = typeof value === "string" ? new Date(value) : value;
+  const d = parseDateUTC(value);
   if (isNaN(d.getTime())) return "";
 
   const now = Date.now();
diff --git a/frontend/src/routes/dashboards/[id]/validation/+page.svelte b/frontend/src/routes/dashboards/[id]/validation/+page.svelte
index 5819b0df..41445f07 100644
--- a/frontend/src/routes/dashboards/[id]/validation/+page.svelte
+++ b/frontend/src/routes/dashboards/[id]/validation/+page.svelte
@@ -14,7 +14,7 @@ import { SvelteURLSearchParams } from "svelte/reactivity";
 	import { goto } from '$app/navigation';
 	import { ROUTES } from '$lib/routes.js';
 	import { t } from '$lib/i18n/index.svelte.js';
-	import { formatDateTime } from "$lib/utils/dateFormat";
+	import { formatDateTime, parseDateUTC } from "$lib/utils/dateFormat";
 	import { EmptyState } from '$lib/ui';
 
 	/** @type {{ data: import('./$types').PageData }} */
@@ -47,8 +47,8 @@ import { SvelteURLSearchParams } from "svelte/reactivity";
 
 	function formatDuration(started: string | null, finished: string | null): string {
 		if (!started) return '—';
-		const start = new Date(started).getTime();
-		const end = finished ? new Date(finished).getTime() : Date.now();
+		const start = parseDateUTC(started).getTime();
+		const end = finished ? parseDateUTC(finished).getTime() : Date.now();
 		const ms = end - start;
 		if (ms < 1000) return `${ms}ms`;
 		if (ms < 60000) return `${(ms / 1000).toFixed(1)}s`;
diff --git a/frontend/src/routes/dashboards/dashboard-helpers.ts b/frontend/src/routes/dashboards/dashboard-helpers.ts
index 89285bd7..9c3806b8 100644
--- a/frontend/src/routes/dashboards/dashboard-helpers.ts
+++ b/frontend/src/routes/dashboards/dashboard-helpers.ts
@@ -2,9 +2,11 @@
 // @BRIEF Shared helper functions for dashboard views — date formatting, pagination, sort indicators.
 // @LAYER lib
 
+import { parseDateUTC } from "$lib/utils/dateFormat";
+
 export function formatDate(value: string | number | Date | null | undefined): string {
   if (!value) return "-";
-  const parsed = new Date(value);
+  const parsed = parseDateUTC(value);
   if (Number.isNaN(parsed.getTime())) return "-";
   return `${parsed.toLocaleDateString()} ${parsed.toLocaleTimeString([], { hour: "2-digit", minute: "2-digit" })}`;
 }
diff --git a/frontend/src/routes/dashboards/health/+page.svelte b/frontend/src/routes/dashboards/health/+page.svelte
index 14c05996..9cea7eb6 100644
--- a/frontend/src/routes/dashboards/health/+page.svelte
+++ b/frontend/src/routes/dashboards/health/+page.svelte
@@ -20,13 +20,14 @@
   import { formatDistanceToNow } from 'date-fns';
   import { EmptyState } from '$lib/ui';
   import { HealthCenterModel } from '$lib/models/HealthCenterModel.svelte.ts';
+  import { parseDateUTC } from "$lib/utils/dateFormat.js";
 
   const m = new HealthCenterModel();
 
   onMount(() => { m.loadData(); });
 
   function formatRelativeDate(ts: string): string {
-    return formatDistanceToNow(new Date(ts), { addSuffix: true });
+    return formatDistanceToNow(parseDateUTC(ts), { addSuffix: true });
   }
 
   function getStatusBadge(status: string): string {
diff --git a/frontend/src/routes/datasets/[id]/+page.svelte b/frontend/src/routes/datasets/[id]/+page.svelte
index 1a3cad38..07b92e7b 100644
--- a/frontend/src/routes/datasets/[id]/+page.svelte
+++ b/frontend/src/routes/datasets/[id]/+page.svelte
@@ -14,6 +14,8 @@
   import { t } from '$lib/i18n/index.svelte.js';
   import { Button, Icon, Skeleton } from '$lib/ui';
   import { DatasetDetailModel } from '$lib/models/DatasetDetailModel.svelte';
+  import { parseDateUTC } from "$lib/utils/dateFormat.js";
+  import { appTimezone } from "$lib/stores/timezone.svelte.js";
 
   let datasetId = $derived(page.params.id);
   let envId = $derived(page.url.searchParams.get('env_id') || '');
@@ -117,13 +119,13 @@
         {#if model.dataset.created_on}
           <div class="flex justify-between py-2 border-b border-border">
             <span class="text-sm text-text-muted">{$t.datasets?.created}</span>
-            <span class="text-sm font-medium text-text">{new Date(model.dataset.created_on).toLocaleDateString()}</span>
+            <span class="text-sm font-medium text-text">{parseDateUTC(model.dataset.created_on).toLocaleDateString(undefined, { timeZone: appTimezone.current })}</span>
           </div>
         {/if}
         {#if model.dataset.changed_on}
           <div class="flex justify-between py-2">
             <span class="text-sm text-text-muted">{$t.datasets?.updated}</span>
-            <span class="text-sm font-medium text-text">{new Date(model.dataset.changed_on).toLocaleDateString()}</span>
+            <span class="text-sm font-medium text-text">{parseDateUTC(model.dataset.changed_on).toLocaleDateString(undefined, { timeZone: appTimezone.current })}</span>
           </div>
         {/if}
       </div>
diff --git a/frontend/src/routes/settings/SystemSettings.svelte b/frontend/src/routes/settings/SystemSettings.svelte
index 6107daca..f4455db6 100644
--- a/frontend/src/routes/settings/SystemSettings.svelte
+++ b/frontend/src/routes/settings/SystemSettings.svelte
@@ -6,9 +6,18 @@
 <script lang="ts">
   import { t, locale } from "$lib/i18n/index.svelte.js";
   import ApiKeysTab from "$lib/components/settings/ApiKeysTab.svelte";
+  import { appTimezone } from "$lib/stores/timezone.svelte.js";
 
   let { settings = $bindable(), onSave } = $props();
 
+  async function handleSave() {
+    // Sync app timezone to global store before persisting
+    if (settings.app_timezone) {
+      appTimezone.current = settings.app_timezone;
+    }
+    if (onSave) await onSave();
+  }
+
   // Common IANA timezones for selection
   const COMMON_TIMEZONES = [
     { value: "Europe/Moscow", label: "Europe/Moscow (MSK, UTC+3)" },
@@ -77,7 +86,7 @@
 
       <div class="mt-6 flex justify-end">
         <button
-          onclick={onSave}
+          onclick={handleSave}
           class="bg-primary text-white px-4 py-2 rounded hover:bg-primary-hover"
         >
           {$t.settings?.save_system || $t.settings?.save_logging || "Save"}
diff --git a/frontend/src/routes/settings/automation/+page.svelte b/frontend/src/routes/settings/automation/+page.svelte
index 0f1292fe..11553838 100644
--- a/frontend/src/routes/settings/automation/+page.svelte
+++ b/frontend/src/routes/settings/automation/+page.svelte
@@ -25,6 +25,8 @@
   import { addToast } from '$lib/toasts.svelte.js';
   import { log } from '$lib/cot-logger';
   import { t } from '$lib/i18n/index.svelte.js';
+  import { parseDateUTC } from "$lib/utils/dateFormat.js";
+  import { appTimezone } from "$lib/stores/timezone.svelte.js";
 
   let policies = $state([]);
   let environments = $state([]);
@@ -250,7 +252,7 @@
                     </span>
                     {#if ts.last_run_at}
                       <span class="text-xs text-text-muted dark:text-text-subtle whitespace-nowrap">
-                        {($t.settings?.last_run || 'Last: {date}').replace('{date}', new Date(ts.last_run_at).toLocaleString())}
+                        {($t.settings?.last_run || 'Last: {date}').replace('{date}', parseDateUTC(ts.last_run_at).toLocaleString(undefined, { timeZone: appTimezone.current }))}
                       </span>
                     {/if}
                   </div>
diff --git a/frontend/src/routes/translate/+page.svelte b/frontend/src/routes/translate/+page.svelte
index af240dde..e78c00ee 100644
--- a/frontend/src/routes/translate/+page.svelte
+++ b/frontend/src/routes/translate/+page.svelte
@@ -8,6 +8,8 @@
   import { addToast } from '$lib/toasts.svelte.js';
   import { Badge, Button, EmptyState, Icon, Pagination } from '$lib/ui';
   import { fetchJobs, deleteJob, duplicateJob } from '$lib/api/translate.js';
+  import { parseDateUTC } from '$lib/utils/dateFormat';
+  import { appTimezone } from '$lib/stores/timezone.svelte.js';
 
   /** @type {string} idle | loading | empty | populated | error */
   let uxState = $state('idle');
@@ -228,7 +230,7 @@
                   <span>{$t.translate?.jobs?.by_label.replace('{by}', job.created_by)}</span>
                 {/if}
                 {#if job.updated_at}
-                  <span>{$t.translate?.jobs?.updated_label.replace('{date}', new Date(job.updated_at).toLocaleDateString())}</span>
+                  <span>{$t.translate?.jobs?.updated_label.replace('{date}', parseDateUTC(job.updated_at).toLocaleDateString(undefined, { timeZone: appTimezone.current }))}</span>
                 {/if}
               </div>
             </div>
diff --git a/frontend/src/routes/translate/history/+page.svelte b/frontend/src/routes/translate/history/+page.svelte
index fdca75b0..ff43449b 100644
--- a/frontend/src/routes/translate/history/+page.svelte
+++ b/frontend/src/routes/translate/history/+page.svelte
@@ -8,6 +8,8 @@
   import { t, _ } from '$lib/i18n/index.svelte.js';
   import { EmptyState, Icon, Pagination } from '$lib/ui';
   import { TranslateHistoryModel } from '$lib/models/TranslateHistoryModel.svelte';
+  import { parseDateUTC } from '$lib/utils/dateFormat';
+  import { appTimezone } from '$lib/stores/timezone.svelte.js';
 
   const m = new TranslateHistoryModel();
 
@@ -99,7 +101,7 @@
                 {#if run.trigger_type}<span class="text-xs text-text-subtle bg-surface-muted px-2 py-0.5 rounded">{run.trigger_type}</span>{/if}
               </div>
               <div class="flex items-center gap-3 text-xs text-text-subtle">
-                <span>{run.created_at ? new Date(run.created_at as string).toLocaleString() : ''}</span>
+                <span>{run.created_at ? parseDateUTC(run.created_at as string).toLocaleString(undefined, { timeZone: appTimezone.current }) : ''}</span>
                 <span>{_('translate.history.records_label').replace('{count}', String(run.total_records || 0))}</span>
                 <span>{_('translate.history.ok_label').replace('{count}', String(run.successful_records || 0))}</span>
                 <span>{_('translate.history.fail_label').replace('{count}', String(run.failed_records || 0))}</span>
@@ -162,8 +164,8 @@
         <div class="grid grid-cols-2 gap-4 mb-6">
           <div><p class="text-xs text-text-muted uppercase">{$t.translate?.history?.status}</p><span class="inline-flex px-2 py-1 text-sm rounded-full {m.getStatusClass(m.selectedRunDetail.status as string)}">{m.selectedRunDetail.status}</span></div>
           <div><p class="text-xs text-text-muted uppercase">{$t.translate?.history?.trigger}</p><p class="text-sm font-medium text-text">{m.selectedRunDetail.trigger_type || 'manual'}</p></div>
-          <div><p class="text-xs text-text-muted uppercase">{$t.translate?.history?.started}</p><p class="text-sm text-text">{m.selectedRunDetail.started_at ? new Date(m.selectedRunDetail.started_at as string).toLocaleString() : '-'}</p></div>
-          <div><p class="text-xs text-text-muted uppercase">{$t.translate?.history?.completed}</p><p class="text-sm text-text">{m.selectedRunDetail.completed_at ? new Date(m.selectedRunDetail.completed_at as string).toLocaleString() : '-'}</p></div>
+          <div><p class="text-xs text-text-muted uppercase">{$t.translate?.history?.started}</p><p class="text-sm text-text">{m.selectedRunDetail.started_at ? parseDateUTC(m.selectedRunDetail.started_at as string).toLocaleString(undefined, { timeZone: appTimezone.current }) : '-'}</p></div>
+          <div><p class="text-xs text-text-muted uppercase">{$t.translate?.history?.completed}</p><p class="text-sm text-text">{m.selectedRunDetail.completed_at ? parseDateUTC(m.selectedRunDetail.completed_at as string).toLocaleString(undefined, { timeZone: appTimezone.current }) : '-'}</p></div>
         </div>
         <!-- Stats -->
         <div class="grid grid-cols-5 gap-3 mb-6">
@@ -226,7 +228,7 @@
                 <div class="flex items-center gap-2 text-xs text-text-muted bg-surface-muted rounded px-2 py-1">
                   <span class="font-medium text-text">{(evt as Record<string, unknown>).event_type}</span>
                   <span class="text-text-subtle">|</span>
-                  <span>{(evt as Record<string, unknown>).created_at ? new Date((evt as Record<string, unknown>).created_at as string).toLocaleString() : ''}</span>
+                   <span>{(evt as Record<string, unknown>).created_at ? parseDateUTC((evt as Record<string, unknown>).created_at as string).toLocaleString(undefined, { timeZone: appTimezone.current }) : ''}</span>
                 </div>
               {/each}
             </div></div>
diff --git a/frontend/src/routes/validation-tasks/+page.svelte b/frontend/src/routes/validation-tasks/+page.svelte
index c3429517..b0e9d77c 100644
--- a/frontend/src/routes/validation-tasks/+page.svelte
+++ b/frontend/src/routes/validation-tasks/+page.svelte
@@ -12,6 +12,8 @@
   import { t } from '$lib/i18n/index.svelte.js';
   import { EmptyState, Pagination, Skeleton, Icon } from '$lib/ui';
   import { ValidationTasksListModel } from '$lib/models/ValidationTasksListModel.svelte';
+  import { parseDateUTC } from "$lib/utils/dateFormat.js";
+  import { appTimezone } from "$lib/stores/timezone.svelte.js";
 
   let { data } = $props();
 
@@ -29,7 +31,7 @@
 
   function formatTimestamp(ts: unknown): string {
     if (!ts) return '\u2014';
-    try { return new Date(ts as string).toLocaleString(); }
+    try { return parseDateUTC(ts as string).toLocaleString(undefined, { timeZone: appTimezone.current }); }
     catch { return String(ts); }
   }
 
diff --git a/frontend/src/routes/validation-tasks/[policyId]/+page.svelte b/frontend/src/routes/validation-tasks/[policyId]/+page.svelte
index 9b46b89c..8ce20646 100644
--- a/frontend/src/routes/validation-tasks/[policyId]/+page.svelte
+++ b/frontend/src/routes/validation-tasks/[policyId]/+page.svelte
@@ -18,6 +18,8 @@
 	import { addToast } from '$lib/toasts.svelte.js';
 	import { triggerValidationRun as triggerRun, deleteValidationTask as deleteTask, getValidationRuns as fetchRuns } from '$lib/api.js';
 	import { page } from '$app/state';
+	import { parseDateUTC } from "$lib/utils/dateFormat.js";
+	import { appTimezone } from "$lib/stores/timezone.svelte.js";
 
 	/** @type {{ data: import('./$types').PageData }} */
 	let { data } = $props();
@@ -179,12 +181,12 @@
 					{/if}
 					{#if task?.created_at}
 						<span>
-							{$t.validation?.created_at || 'Created'}: {new Date(task.created_at).toLocaleString()}
+							{$t.validation?.created_at || 'Created'}: {parseDateUTC(task.created_at).toLocaleString(undefined, { timeZone: appTimezone.current })}
 						</span>
 					{/if}
 					{#if task?.updated_at}
 						<span>
-							{$t.validation?.updated_at || 'Updated'}: {new Date(task.updated_at).toLocaleString()}
+							{$t.validation?.updated_at || 'Updated'}: {parseDateUTC(task.updated_at).toLocaleString(undefined, { timeZone: appTimezone.current })}
 						</span>
 					{/if}
 				</div>
@@ -311,7 +313,7 @@
 						>
 							<td class="px-4 py-3 whitespace-nowrap text-sm text-text-muted">
 								{run.timestamp || run.started_at || run.created_at
-									? new Date(run.timestamp || run.started_at || run.created_at).toLocaleString()
+									? parseDateUTC(run.timestamp || run.started_at || run.created_at).toLocaleString(undefined, { timeZone: appTimezone.current })
 									: '-'}
 							</td>
 							<td class="px-4 py-3 whitespace-nowrap text-sm text-text-muted">
diff --git a/frontend/src/routes/validation-tasks/[policyId]/runs/[runId]/+page.svelte b/frontend/src/routes/validation-tasks/[policyId]/runs/[runId]/+page.svelte
index 57a512a7..73ecb906 100644
--- a/frontend/src/routes/validation-tasks/[policyId]/runs/[runId]/+page.svelte
+++ b/frontend/src/routes/validation-tasks/[policyId]/runs/[runId]/+page.svelte
@@ -10,6 +10,8 @@
   import { page } from '$app/state';
   import { EmptyState, Icon } from '$lib/ui';
   import { ValidationRunDetailModel } from '$lib/models/ValidationRunDetailModel.svelte';
+  import { parseDateUTC } from "$lib/utils/dateFormat.js";
+  import { appTimezone } from "$lib/stores/timezone.svelte.js";
 
   let { data } = $props();
 
@@ -70,9 +72,9 @@
         <span class="font-semibold text-text">{m.run.id}</span>
         <span class="inline-flex px-2 py-0.5 text-xs rounded-full {getStatusDotClass(m.run.status)}">{getStatusDot(m.run.status)} {m.run.status}</span>
         {#if m.run.trigger_type}<span class="text-text-muted">{getTriggerLabel(m.run.trigger_type, _)}</span>{/if}
-        <span class="text-text-subtle">{m.run.started_at ? new Date(m.run.started_at as string).toLocaleString() : ''}</span>
-        {#if m.run.finished_at}<span class="text-text-subtle">→ {new Date(m.run.finished_at as string).toLocaleString()}</span>{/if}
-        {#if m.run.started_at && m.run.finished_at}<span class="text-text-muted font-mono text-xs">{formatDuration((new Date(m.run.finished_at as string).getTime() - new Date(m.run.started_at as string).getTime()))}</span>{/if}
+        <span class="text-text-subtle">{m.run.started_at ? parseDateUTC(m.run.started_at as string).toLocaleString(undefined, { timeZone: appTimezone.current }) : ''}</span>
+        {#if m.run.finished_at}<span class="text-text-subtle">→ {parseDateUTC(m.run.finished_at as string).toLocaleString(undefined, { timeZone: appTimezone.current })}</span>{/if}
+        {#if m.run.started_at && m.run.finished_at}<span class="text-text-muted font-mono text-xs">{formatDuration((parseDateUTC(m.run.finished_at as string).getTime() - parseDateUTC(m.run.started_at as string).getTime()))}</span>{/if}
       </div>
     </div>
 
@@ -177,7 +179,7 @@
                       <tbody class="divide-y divide-border">
                         {#each (dashboard as Record<string,unknown>).task_logs as logEntry}
                           <tr>
-                            <td class="px-3 py-2 align-top text-text-muted">{new Date((logEntry as Record<string,unknown>).timestamp as string).toLocaleString()}</td>
+                            <td class="px-3 py-2 align-top text-text-muted">{parseDateUTC((logEntry as Record<string,unknown>).timestamp as string).toLocaleString(undefined, { timeZone: appTimezone.current })}</td>
                             <td class="px-3 py-2 align-top text-text">{(logEntry as Record<string,unknown>).level || '-'}</td>
                             <td class="px-3 py-2 align-top text-text">{(logEntry as Record<string,unknown>).source || '-'}</td>
                             <td class="px-3 py-2 align-top text-text whitespace-pre-wrap">{(logEntry as Record<string,unknown>).message || '-'}</td>
diff --git a/frontend/src/routes/validation-tasks/history/+page.svelte b/frontend/src/routes/validation-tasks/history/+page.svelte
index 2a624045..0e39db53 100644
--- a/frontend/src/routes/validation-tasks/history/+page.svelte
+++ b/frontend/src/routes/validation-tasks/history/+page.svelte
@@ -6,7 +6,7 @@
 import { SvelteURLSearchParams } from "svelte/reactivity";
 	import { goto } from '$app/navigation';
 	import { t } from '$lib/i18n/index.svelte.js';
-	import { formatDateTime } from "$lib/utils/dateFormat";
+	import { formatDateTime, parseDateUTC } from "$lib/utils/dateFormat";
 	import { Pagination } from '$lib/ui';
 
 	/** @type {{ data: import('./$types').PageData }} */
@@ -47,8 +47,8 @@ import { SvelteURLSearchParams } from "svelte/reactivity";
 
 	function formatDuration(started: string | null, finished: string | null): string {
 		if (!started) return '—';
-		const start = new Date(started).getTime();
-		const end = finished ? new Date(finished).getTime() : Date.now();
+		const start = parseDateUTC(started).getTime();
+		const end = finished ? parseDateUTC(finished).getTime() : Date.now();
 		const ms = end - start;
 		if (ms < 1000) return `${ms}ms`;
 		if (ms < 60000) return `${(ms / 1000).toFixed(1)}s`;