diff --git a/web/src/chat/presentation.test.ts b/web/src/chat/presentation.test.ts
index e444b5f5..efa45320 100644
--- a/web/src/chat/presentation.test.ts
+++ b/web/src/chat/presentation.test.ts
@@ -167,8 +167,13 @@ describe('formatResetTime', () => {
 describe('formatMessageTimestamp', () => {
     it('formats today without requiring a date prefix', () => {
         const now = new Date(2026, 4, 22, 14, 30)
-        const result = formatMessageTimestamp(new Date(2026, 4, 22, 9, 5), now)
-        expect(result).toBeTruthy()
+        const date = new Date(2026, 4, 22, 9, 5)
+        const result = formatMessageTimestamp(date, now)
+        expect(result).toBe(date.toLocaleTimeString(undefined, {
+            hour: '2-digit',
+            minute: '2-digit',
+            hourCycle: 'h23'
+        }))
         expect(result).not.toContain('2026')
     })
 
diff --git a/web/src/chat/presentation.ts b/web/src/chat/presentation.ts
index 28a750ce..823c0595 100644
--- a/web/src/chat/presentation.ts
+++ b/web/src/chat/presentation.ts
@@ -32,15 +32,15 @@ export function formatMessageTimestamp(date: Date, now: Date = new Date()): stri
         && date.getDate() === now.getDate()
 
     if (sameDay) {
-        return date.toLocaleTimeString(undefined, { hour: 'numeric', minute: '2-digit' })
+        return date.toLocaleTimeString(undefined, { hour: '2-digit', minute: '2-digit', hourCycle: 'h23' })
     }
 
     const sameYear = date.getFullYear() === now.getFullYear()
     if (sameYear) {
-        return date.toLocaleString(undefined, { month: 'short', day: 'numeric', hour: 'numeric', minute: '2-digit' })
+        return date.toLocaleString(undefined, { month: 'short', day: 'numeric', hour: '2-digit', minute: '2-digit', hourCycle: 'h23' })
     }
 
-    return date.toLocaleString(undefined, { year: 'numeric', month: 'short', day: 'numeric', hour: 'numeric', minute: '2-digit' })
+    return date.toLocaleString(undefined, { year: 'numeric', month: 'short', day: 'numeric', hour: '2-digit', minute: '2-digit', hourCycle: 'h23' })
 }
 
 export function formatMessageTimestampTitle(date: Date): string {
diff --git a/web/src/components/AssistantChat/messages/MessageTimestamp.tsx b/web/src/components/AssistantChat/messages/MessageTimestamp.tsx
index 650bd51e..fdc245ef 100644
--- a/web/src/components/AssistantChat/messages/MessageTimestamp.tsx
+++ b/web/src/components/AssistantChat/messages/MessageTimestamp.tsx
@@ -1,5 +1,6 @@
 import { useAssistantState } from '@assistant-ui/react'
 import { formatMessageTimestamp, formatMessageTimestampTitle } from '@/chat/presentation'
+import { cn } from '@/lib/utils'
 
 type MessageTimestampProps = {
     className?: string
@@ -12,7 +13,7 @@ export function MessageTimestamp(props: MessageTimestampProps) {
         <time
             dateTime={createdAt.toISOString()}
             title={formatMessageTimestampTitle(createdAt)}
-            className={props.className}
+            className={cn('tabular-nums', props.className)}
         >
             {formatMessageTimestamp(createdAt)}
         </time>
diff --git a/web/src/components/SessionList.tsx b/web/src/components/SessionList.tsx
index 70e3d9c7..66f233d7 100644
--- a/web/src/components/SessionList.tsx
+++ b/web/src/components/SessionList.tsx
@@ -730,7 +730,10 @@ function SessionListSearch(props: {
     )
 }
 
-function formatCodexImportedRelativeTime(value: number, t: (key: string, params?: Record<string, string | number>) => string): string | null {
+function formatCodexImportedRelativeTime(
+    value: number,
+    t: (key: string, params?: Record<string, string | number>) => string
+): string | null {
     const ms = value < 1_000_000_000_000 ? value * 1000 : value
     if (!Number.isFinite(ms)) return null
     const delta = Date.now() - ms
@@ -741,10 +744,13 @@ function formatCodexImportedRelativeTime(value: number, t: (key: string, params?
     if (hours < 24) return t('session.time.importedFromCodex.hoursAgo', { n: hours })
     const days = Math.floor(hours / 24)
     if (days < 7) return t('session.time.importedFromCodex.daysAgo', { n: days })
-    return new Date(ms).toLocaleDateString()
+    return formatRelativeTime(value, t)
 }
 
-function getSessionTimeLabel(session: SessionSummary, t: (key: string, params?: Record<string, string | number>) => string): string | null {
+function getSessionTimeLabel(
+    session: SessionSummary,
+    t: (key: string, params?: Record<string, string | number>) => string
+): string | null {
     const codexSessionId = session.metadata?.agentSessionId
     const importedAt = session.metadata?.flavor === 'codex'
         ? getCodexImportedAt(codexSessionId)
@@ -904,7 +910,7 @@ function SessionItem(props: {
                                 {t('session.item.pending')} {s.pendingRequestsCount}
                             </span>
                         ) : null}
-                        <span className="text-[var(--app-hint)]">
+                        <span className="tabular-nums text-[var(--app-hint)]">
                             {getSessionTimeLabel(s, t)}
                         </span>
                     </div>
diff --git a/web/src/lib/relativeTime.test.ts b/web/src/lib/relativeTime.test.ts
new file mode 100644
index 00000000..24f49e4e
--- /dev/null
+++ b/web/src/lib/relativeTime.test.ts
@@ -0,0 +1,23 @@
+import { afterEach, describe, expect, it, vi } from 'vitest'
+import { formatRelativeTime, formatSessionListDate } from '@/lib/relativeTime'
+
+const t = (key: string) => key
+
+afterEach(() => {
+    vi.useRealTimers()
+})
+
+describe('formatSessionListDate', () => {
+    it('zero-pads months and days', () => {
+        expect(formatSessionListDate(new Date(2026, 6, 7))).toBe('2026/07/07')
+    })
+})
+
+describe('formatRelativeTime', () => {
+    it('uses the padded date after the relative-time window', () => {
+        vi.useFakeTimers()
+        vi.setSystemTime(new Date(2026, 6, 21, 12, 0))
+
+        expect(formatRelativeTime(new Date(2026, 6, 7, 9, 0).getTime(), t)).toBe('2026/07/07')
+    })
+})
diff --git a/web/src/lib/relativeTime.ts b/web/src/lib/relativeTime.ts
index 31abbb13..ac014256 100644
--- a/web/src/lib/relativeTime.ts
+++ b/web/src/lib/relativeTime.ts
@@ -1,3 +1,10 @@
+export function formatSessionListDate(date: Date): string {
+    const year = String(date.getFullYear())
+    const month = String(date.getMonth() + 1).padStart(2, '0')
+    const day = String(date.getDate()).padStart(2, '0')
+    return `${year}/${month}/${day}`
+}
+
 /**
  * Formats an epoch ms / s value as a localised "Nm ago" / "Nh ago" / date label.
  * Accepts both ms and seconds; values smaller than 1e12 are treated as seconds.
@@ -18,5 +25,5 @@ export function formatRelativeTime(
     if (hours < 24) return t('session.time.hoursAgo', { n: hours })
     const days = Math.floor(hours / 24)
     if (days < 7) return t('session.time.daysAgo', { n: days })
-    return new Date(ms).toLocaleDateString()
+    return formatSessionListDate(new Date(ms))
 }