feat: show relative timestamps with the exact time on hover

Device and API key cards rendered full timestamps ("Registered at: May 18,
2023, 1:42 PM"), which wrapped and dominated the cards at 375px.

New shared RelativeTime renders "7 days ago" with the exact date and time in a
tooltip. Formatting is delegated to date-fns, already a dependency and already
used by the webhook table, so no new package and no hand-rolled date parsing.
The only local rule is a "Just now" threshold under one minute.

Details:
- formatDistanceToNowStrict, not formatDistanceToNow, so it reads "3 minutes
  ago" rather than "about 3 minutes ago".
- Renders a real <time dateTime> element, keeping the machine-readable value
  in the DOM.
- The trigger is focusable, so the exact time is reachable by keyboard and not
  hover-only.
- Invalid or missing values render a caller-supplied fallback, so a key that
  has never been used still reads "Last used never" instead of "Invalid Date".

Labels shortened to match: "Registered at:" to "Registered", "Created at:" to
"Created".

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

web/app/(app)/dashboard/(components)/api-keys.tsx

@@ -29,6 +29,7 @@ import {
 } from '@/lib/api'
 import { Skeleton } from '@/components/ui/skeleton'
 import EmptyState from '@/components/shared/empty-state'
+import RelativeTime from '@/components/shared/relative-time'
 import GenerateApiKey, {
   type GenerateApiKeyHandle,
 } from './generate-api-key'
@@ -217,23 +218,18 @@ export default function ApiKeys() {
                     </div>
                     <div className='flex items-center mt-1 space-x-3 text-xs text-muted-foreground'>
                       <div>
-                        Created at:{' '}
-                        {new Date(apiKey.createdAt).toLocaleString('en-US', {
-                          dateStyle: 'medium',
-                          timeStyle: 'short',
-                        })}
+                        Created <RelativeTime value={apiKey.createdAt} />
                       </div>
                       <div>
-                        Last used:{' '}
-                        {apiKey?.lastUsedAt && apiKey.usageCount
-                          ? new Date(apiKey.lastUsedAt).toLocaleString(
-                              'en-US',
-                              {
-                                dateStyle: 'medium',
-                                timeStyle: 'short',
-                              }
-                            )
-                          : 'Never'}
+                        Last used{' '}
+                        <RelativeTime
+                          value={
+                            apiKey?.lastUsedAt && apiKey.usageCount
+                              ? apiKey.lastUsedAt
+                              : null
+                          }
+                          fallback='never'
+                        />
                       </div>
                     </div>
                   </div>
@@ -351,13 +347,7 @@ export default function ApiKeys() {
                       {k.apiKey}
                     </code>
                     <div className='text-xs text-muted-foreground mt-1'>
-                      Revoked{' '}
-                      {k.revokedAt
-                        ? new Date(k.revokedAt).toLocaleString('en-US', {
-                            dateStyle: 'medium',
-                            timeStyle: 'short',
-                          })
-                        : ''}
+                      Revoked <RelativeTime value={k.revokedAt} fallback='' />
                     </div>
                   </div>
                   <Button

web/app/(app)/dashboard/(components)/device-list.tsx

@@ -17,6 +17,7 @@ import { useToast } from '@/hooks/use-toast'
 import { Routes } from '@/config/routes'
 import { useDeleteDevice, useDevices, useSubscription } from '@/lib/api'
 import EmptyState from '@/components/shared/empty-state'
+import RelativeTime from '@/components/shared/relative-time'
 import { useRef, useState } from 'react'
 import {
   Dialog,
@@ -256,11 +257,7 @@ export default function DeviceList() {
                           'unknown'}
                       </div>
                       <div>
-                        Registered at:{' '}
-                        {new Date(device.createdAt).toLocaleString('en-US', {
-                          dateStyle: 'medium',
-                          timeStyle: 'short',
-                        })}
+                        Registered <RelativeTime value={device.createdAt} />
                       </div>
                     </div>
                     {isDeviceOutdated(device as DeviceVersionCandidate) && (

web/components/shared/relative-time.test.tsx

@@ -0,0 +1,61 @@
+import { describe, expect, it } from 'vitest'
+import { render, screen } from '@testing-library/react'
+import RelativeTime, { toExactLabel, toRelativeLabel } from './relative-time'
+
+const NOW = new Date('2026-07-18T12:00:00.000Z')
+const ago = (ms: number) => new Date(NOW.getTime() - ms)
+
+const SECOND = 1000
+const MINUTE = 60 * SECOND
+const HOUR = 60 * MINUTE
+const DAY = 24 * HOUR
+
+describe('toRelativeLabel', () => {
+  it('collapses anything under a minute to "Just now"', () => {
+    expect(toRelativeLabel(ago(0), NOW)).toBe('Just now')
+    expect(toRelativeLabel(ago(45 * SECOND), NOW)).toBe('Just now')
+  })
+
+  it('is strict, so it does not say "about"', () => {
+    // formatDistanceToNow would render "about 3 minutes ago".
+    expect(toRelativeLabel(ago(3 * MINUTE), NOW)).not.toContain('about')
+  })
+})
+
+describe('RelativeTime', () => {
+  it('renders a relative label for a past date', () => {
+    render(<RelativeTime value={ago(7 * DAY)} />)
+    expect(screen.getByText('7 days ago')).toBeInTheDocument()
+  })
+
+  it('exposes the machine-readable timestamp on a <time> element', () => {
+    const value = ago(2 * DAY)
+    const { container } = render(<RelativeTime value={value} />)
+    const el = container.querySelector('time')
+    expect(el).toBeInTheDocument()
+    expect(el).toHaveAttribute('dateTime', value.toISOString())
+  })
+
+  it('is reachable by keyboard so the exact time is not hover-only', () => {
+    const { container } = render(<RelativeTime value={ago(DAY)} />)
+    expect(container.querySelector('time')).toHaveAttribute('tabindex', '0')
+  })
+
+  it('renders the fallback for a null value', () => {
+    render(<RelativeTime value={null} fallback='Never' />)
+    expect(screen.getByText('Never')).toBeInTheDocument()
+    expect(document.querySelector('time')).toBeNull()
+  })
+
+  it('renders the fallback for an unparseable value rather than "Invalid Date"', () => {
+    render(<RelativeTime value='not-a-date' fallback='Unknown' />)
+    expect(screen.getByText('Unknown')).toBeInTheDocument()
+  })
+
+  it('formats the exact label with both date and time', () => {
+    // Constructed from parts so the assertion does not depend on the TZ the
+    // suite happens to run in.
+    const date = new Date(2023, 4, 18, 13, 42)
+    expect(toExactLabel(date)).toBe('May 18, 2023 at 1:42 PM')
+  })
+})

web/components/shared/relative-time.tsx

@@ -0,0 +1,71 @@
+'use client'
+
+import { format, formatDistanceToNowStrict, isValid } from 'date-fns'
+import {
+  Tooltip,
+  TooltipContent,
+  TooltipProvider,
+  TooltipTrigger,
+} from '@/components/ui/tooltip'
+import { cn } from '@/lib/utils'
+
+// Anything under this reads as "Just now" rather than "34 seconds ago".
+const JUST_NOW_MS = 60 * 1000
+
+export function toRelativeLabel(date: Date, now: Date = new Date()): string {
+  if (now.getTime() - date.getTime() < JUST_NOW_MS) return 'Just now'
+  // Strict, so it says "3 minutes ago" instead of "about 3 minutes ago".
+  return formatDistanceToNowStrict(date, { addSuffix: true })
+}
+
+export function toExactLabel(date: Date): string {
+  return format(date, "MMM d, yyyy 'at' h:mm a")
+}
+
+/**
+ * A timestamp shown as "7 days ago", with the exact date and time on hover.
+ *
+ * Long absolute timestamps ("May 18, 2023, 1:42 PM") wrapped and dominated the
+ * device and API key cards at mobile widths. Formatting is delegated to
+ * date-fns; the only local rule is the "Just now" threshold.
+ */
+export default function RelativeTime({
+  value,
+  fallback = '-',
+  className,
+}: {
+  value: string | number | Date | null | undefined
+  fallback?: string
+  className?: string
+}) {
+  if (value === null || value === undefined || value === '') {
+    return <span className={className}>{fallback}</span>
+  }
+
+  const date = value instanceof Date ? value : new Date(value)
+  if (!isValid(date)) {
+    return <span className={className}>{fallback}</span>
+  }
+
+  return (
+    <TooltipProvider delayDuration={200}>
+      <Tooltip>
+        <TooltipTrigger asChild>
+          {/* A real <time> keeps the machine-readable value in the DOM, and
+              tabIndex means keyboard users can reach the exact timestamp too. */}
+          <time
+            dateTime={date.toISOString()}
+            tabIndex={0}
+            className={cn(
+              'cursor-default underline decoration-dotted underline-offset-2',
+              className
+            )}
+          >
+            {toRelativeLabel(date)}
+          </time>
+        </TooltipTrigger>
+        <TooltipContent>{toExactLabel(date)}</TooltipContent>
+      </Tooltip>
+    </TooltipProvider>
+  )
+}