Add temporal grouping to event list (Today/This Week/Next Week/Later/Past)

Group events into five temporal sections with section headers, date subheaders,
and context-aware time display (clock time for upcoming, relative for past).
Includes new useEventGrouping composable, SectionHeader and DateSubheader
components, full unit and E2E test coverage.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/src/components/DateSubheader.vue

@@ -0,0 +1,19 @@
+<template>
+  <h3 class="date-subheader">{{ label }}</h3>
+</template>
+
+<script setup lang="ts">
+defineProps<{
+  label: string
+}>()
+</script>
+
+<style scoped>
+.date-subheader {
+  font-size: 0.85rem;
+  font-weight: 500;
+  color: rgba(255, 255, 255, 0.85);
+  margin: 0;
+  padding: var(--spacing-xs) 0;
+}
+</style>

frontend/src/components/EventCard.vue

@@ -9,7 +9,7 @@
   >
     <RouterLink :to="`/events/${eventToken}`" class="event-card__link">
       <span class="event-card__title">{{ title }}</span>
-      <span class="event-card__time">{{ relativeTime }}</span>
+      <span class="event-card__time">{{ displayTime }}</span>
     </RouterLink>
     <span v-if="eventRole" class="event-card__badge" :class="`event-card__badge--${eventRole}`">
       {{ eventRole === 'organizer' ? 'Organizer' : 'Attendee' }}
@@ -35,12 +35,21 @@ const props = defineProps<{
   relativeTime: string
   isPast: boolean
   eventRole?: 'organizer' | 'attendee'
+  timeDisplayMode?: 'clock' | 'relative'
+  dateTime?: string
 }>()
 
 const emit = defineEmits<{
   delete: [eventToken: string]
 }>()
 
+const displayTime = computed(() => {
+  if (props.timeDisplayMode === 'clock' && props.dateTime) {
+    return new Intl.DateTimeFormat(undefined, { hour: '2-digit', minute: '2-digit' }).format(new Date(props.dateTime))
+  }
+  return props.relativeTime
+})
+
 const SWIPE_THRESHOLD = 80
 
 const startX = ref(0)

frontend/src/components/EventList.vue

@@ -1,15 +1,30 @@
 <template>
-  <div class="event-list" role="list" aria-label="Your events">
-    <div v-for="event in sortedEvents" :key="event.eventToken" role="listitem">
-      <EventCard
-        :event-token="event.eventToken"
-        :title="event.title"
-        :relative-time="formatRelativeTime(event.dateTime)"
-        :is-past="isPast(event.dateTime)"
-        :event-role="getRole(event)"
-        @delete="requestDelete"
-      />
-    </div>
+  <div class="event-list">
+    <section
+      v-for="section in groupedSections"
+      :key="section.key"
+      :aria-label="section.label"
+      class="event-section"
+    >
+      <SectionHeader :label="section.label" :emphasized="section.emphasized" />
+      <div role="list">
+        <template v-for="group in section.dateGroups" :key="group.dateKey">
+          <DateSubheader v-if="group.showSubheader" :label="group.label" />
+          <div v-for="event in group.events" :key="event.eventToken" role="listitem">
+            <EventCard
+              :event-token="event.eventToken"
+              :title="event.title"
+              :relative-time="formatRelativeTime(event.dateTime)"
+              :is-past="section.key === 'past'"
+              :event-role="getRole(event)"
+              :time-display-mode="section.key === 'past' ? 'relative' : 'clock'"
+              :date-time="event.dateTime"
+              @delete="requestDelete"
+            />
+          </div>
+        </template>
+      </div>
+    </section>
     <ConfirmDialog
       :open="!!pendingDeleteToken"
       title="Remove event?"
@@ -25,8 +40,11 @@
 <script setup lang="ts">
 import { computed, ref } from 'vue'
 import { useEventStorage, isValidStoredEvent } from '../composables/useEventStorage'
+import { useEventGrouping } from '../composables/useEventGrouping'
 import { formatRelativeTime } from '../composables/useRelativeTime'
 import EventCard from './EventCard.vue'
+import SectionHeader from './SectionHeader.vue'
+import DateSubheader from './DateSubheader.vue'
 import ConfirmDialog from './ConfirmDialog.vue'
 import type { StoredEvent } from '../composables/useEventStorage'
 
@@ -49,29 +67,26 @@ function cancelDelete() {
   pendingDeleteToken.value = null
 }
 
-function isPast(dateTime: string): boolean {
-  return new Date(dateTime) < new Date()
-}
-
 function getRole(event: StoredEvent): 'organizer' | 'attendee' | undefined {
   if (event.organizerToken) return 'organizer'
   if (event.rsvpToken) return 'attendee'
   return undefined
 }
 
-const sortedEvents = computed(() => {
+const groupedSections = computed(() => {
   const valid = getStoredEvents().filter(isValidStoredEvent)
-  const now = new Date()
-  const upcoming = valid.filter((e) => new Date(e.dateTime) >= now)
-  const past = valid.filter((e) => new Date(e.dateTime) < now)
-  upcoming.sort((a, b) => new Date(a.dateTime).getTime() - new Date(b.dateTime).getTime())
-  past.sort((a, b) => new Date(b.dateTime).getTime() - new Date(a.dateTime).getTime())
-  return [...upcoming, ...past]
+  return useEventGrouping(valid)
 })
 </script>
 
 <style scoped>
 .event-list {
+  display: flex;
+  flex-direction: column;
+  gap: var(--spacing-md);
+}
+
+.event-section [role="list"] {
   display: flex;
   flex-direction: column;
   gap: var(--spacing-sm);

frontend/src/components/SectionHeader.vue

@@ -0,0 +1,27 @@
+<template>
+  <h2 class="section-header" :class="{ 'section-header--emphasized': emphasized }">
+    {{ label }}
+  </h2>
+</template>
+
+<script setup lang="ts">
+defineProps<{
+  label: string
+  emphasized?: boolean
+}>()
+</script>
+
+<style scoped>
+.section-header {
+  font-size: 1rem;
+  font-weight: 700;
+  color: var(--color-text);
+  margin: 0;
+  padding: var(--spacing-sm) 0;
+}
+
+.section-header--emphasized {
+  font-size: 1.1rem;
+  font-weight: 800;
+}
+</style>

frontend/src/components/__tests__/DateSubheader.spec.ts

@@ -0,0 +1,17 @@
+import { describe, it, expect } from 'vitest'
+import { mount } from '@vue/test-utils'
+import DateSubheader from '../DateSubheader.vue'
+
+describe('DateSubheader', () => {
+  it('renders the date label as an h3', () => {
+    const wrapper = mount(DateSubheader, { props: { label: 'Wed, 12 Mar' } })
+    const h3 = wrapper.find('h3')
+    expect(h3.exists()).toBe(true)
+    expect(h3.text()).toBe('Wed, 12 Mar')
+  })
+
+  it('applies the date-subheader class', () => {
+    const wrapper = mount(DateSubheader, { props: { label: 'Fri, 14 Mar' } })
+    expect(wrapper.find('.date-subheader').exists()).toBe(true)
+  })
+})

frontend/src/components/__tests__/EventCard.spec.ts

@@ -73,4 +73,28 @@ describe('EventCard', () => {
     await wrapper.find('.event-card__delete').trigger('click')
     expect(wrapper.emitted('delete')).toEqual([['abc-123']])
   })
+
+  it('displays clock time when timeDisplayMode is clock', () => {
+    const wrapper = mountCard({
+      timeDisplayMode: 'clock',
+      dateTime: '2026-03-11T18:30:00',
+    })
+    const timeText = wrapper.find('.event-card__time').text()
+    // Locale-dependent: could be "18:30" or "06:30 PM"
+    expect(timeText).toMatch(/(?:18.30|6.30\s*PM)/i)
+  })
+
+  it('displays relative time when timeDisplayMode is relative', () => {
+    const wrapper = mountCard({
+      relativeTime: '3 days ago',
+      timeDisplayMode: 'relative',
+      dateTime: '2026-03-08T10:00:00',
+    })
+    expect(wrapper.find('.event-card__time').text()).toBe('3 days ago')
+  })
+
+  it('falls back to relativeTime when timeDisplayMode is not set', () => {
+    const wrapper = mountCard({ relativeTime: 'in 3 days' })
+    expect(wrapper.find('.event-card__time').text()).toBe('in 3 days')
+  })
 })

frontend/src/components/__tests__/EventList.spec.ts

@@ -1,4 +1,4 @@
-import { describe, it, expect, vi, beforeEach } from 'vitest'
+import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest'
 import { mount } from '@vue/test-utils'
 import { createRouter, createMemoryHistory } from 'vue-router'
 import EventList from '../EventList.vue'
@@ -11,10 +11,15 @@ const router = createRouter({
   ],
 })
 
+// Fixed "now": Wednesday, 2026-03-11 12:00
+const NOW = new Date(2026, 2, 11, 12, 0, 0)
+
 const mockEvents = [
-  { eventToken: 'past-1', title: 'Past Event', dateTime: '2025-01-01T10:00:00Z', expiryDate: '' },
-  { eventToken: 'future-1', title: 'Future Event', dateTime: '2027-06-15T10:00:00Z', expiryDate: '' },
-  { eventToken: 'future-2', title: 'Soon Event', dateTime: '2027-01-01T10:00:00Z', expiryDate: '' },
+  { eventToken: 'past-1', title: 'Past Event', dateTime: '2026-03-01T10:00:00', expiryDate: '' },
+  { eventToken: 'later-1', title: 'Later Event', dateTime: '2027-06-15T10:00:00', expiryDate: '' },
+  { eventToken: 'today-1', title: 'Today Event', dateTime: '2026-03-11T18:00:00', expiryDate: '' },
+  { eventToken: 'week-1', title: 'This Week Event', dateTime: '2026-03-13T10:00:00', expiryDate: '' },
+  { eventToken: 'nextweek-1', title: 'Next Week Event', dateTime: '2026-03-16T10:00:00', expiryDate: '' },
 ]
 
 vi.mock('../../composables/useEventStorage', () => ({
@@ -33,9 +38,12 @@ vi.mock('../../composables/useEventStorage', () => ({
 
 vi.mock('../../composables/useRelativeTime', () => ({
   formatRelativeTime: (dateTime: string) => {
-    if (dateTime.startsWith('2025')) return '1 year ago'
+    if (dateTime.includes('03-01')) return '10 days ago'
     if (dateTime.includes('06-15')) return 'in 1 year'
-    return 'in 10 months'
+    if (dateTime.includes('03-11')) return 'in 6 hours'
+    if (dateTime.includes('03-13')) return 'in 2 days'
+    if (dateTime.includes('03-16')) return 'in 5 days'
+    return 'sometime'
   },
 }))
 
@@ -48,32 +56,85 @@ function mountList() {
 describe('EventList', () => {
   beforeEach(() => {
     vi.useFakeTimers()
-    vi.setSystemTime(new Date('2026-03-08T12:00:00Z'))
+    vi.setSystemTime(NOW)
   })
 
-  it('renders all valid events', () => {
+  afterEach(() => {
+    vi.useRealTimers()
+  })
+
+  it('renders section headers for each non-empty section', () => {
+    const wrapper = mountList()
+    const headers = wrapper.findAll('.section-header')
+    expect(headers).toHaveLength(5)
+    expect(headers[0]!.text()).toBe('Today')
+    expect(headers[1]!.text()).toBe('This Week')
+    expect(headers[2]!.text()).toBe('Next Week')
+    expect(headers[3]!.text()).toBe('Later')
+    expect(headers[4]!.text()).toBe('Past')
+  })
+
+  it('renders events within their correct sections', () => {
+    const wrapper = mountList()
+    const sections = wrapper.findAll('.event-section')
+    expect(sections).toHaveLength(5)
+
+    expect(sections[0]!.text()).toContain('Today Event')
+    expect(sections[1]!.text()).toContain('This Week Event')
+    expect(sections[2]!.text()).toContain('Next Week Event')
+    expect(sections[3]!.text()).toContain('Later Event')
+    expect(sections[4]!.text()).toContain('Past Event')
+  })
+
+  it('renders all valid events as cards', () => {
     const wrapper = mountList()
     const cards = wrapper.findAll('.event-card')
-    expect(cards).toHaveLength(3)
-  })
-
-  it('sorts upcoming events before past events', () => {
-    const wrapper = mountList()
-    const titles = wrapper.findAll('.event-card__title').map((el) => el.text())
-    // Upcoming events first (sorted ascending), then past events
-    expect(titles[0]).toBe('Soon Event')
-    expect(titles[1]).toBe('Future Event')
-    expect(titles[2]).toBe('Past Event')
+    expect(cards).toHaveLength(5)
   })
 
   it('marks past events with isPast class', () => {
     const wrapper = mountList()
-    const cards = wrapper.findAll('.event-card')
-    expect(cards).toHaveLength(3)
-    // Last card should be past
-    expect(cards[2]!.classes()).toContain('event-card--past')
-    // First two should not be past
+    const pastSection = wrapper.findAll('.event-section')[4]!
+    const pastCards = pastSection.findAll('.event-card')
+    expect(pastCards).toHaveLength(1)
+    expect(pastCards[0]!.classes()).toContain('event-card--past')
+  })
+
+  it('does not mark non-past events with isPast class', () => {
+    const wrapper = mountList()
+    const todaySection = wrapper.findAll('.event-section')[0]!
+    const cards = todaySection.findAll('.event-card')
     expect(cards[0]!.classes()).not.toContain('event-card--past')
-    expect(cards[1]!.classes()).not.toContain('event-card--past')
+  })
+
+  it('sections have aria-label attributes', () => {
+    const wrapper = mountList()
+    const sections = wrapper.findAll('section')
+    expect(sections[0]!.attributes('aria-label')).toBe('Today')
+    expect(sections[1]!.attributes('aria-label')).toBe('This Week')
+    expect(sections[2]!.attributes('aria-label')).toBe('Next Week')
+    expect(sections[3]!.attributes('aria-label')).toBe('Later')
+    expect(sections[4]!.attributes('aria-label')).toBe('Past')
+  })
+
+  it('does not render date subheader in "Today" section', () => {
+    const wrapper = mountList()
+    const todaySection = wrapper.findAll('.event-section')[0]!
+    expect(todaySection.find('.date-subheader').exists()).toBe(false)
+  })
+
+  it('renders date subheaders in non-today sections', () => {
+    const wrapper = mountList()
+    const thisWeekSection = wrapper.findAll('.event-section')[1]!
+    expect(thisWeekSection.find('.date-subheader').exists()).toBe(true)
+
+    const nextWeekSection = wrapper.findAll('.event-section')[2]!
+    expect(nextWeekSection.find('.date-subheader').exists()).toBe(true)
+
+    const laterSection = wrapper.findAll('.event-section')[3]!
+    expect(laterSection.find('.date-subheader').exists()).toBe(true)
+
+    const pastSection = wrapper.findAll('.event-section')[4]!
+    expect(pastSection.find('.date-subheader').exists()).toBe(true)
   })
 })

frontend/src/components/__tests__/SectionHeader.spec.ts

@@ -0,0 +1,27 @@
+import { describe, it, expect } from 'vitest'
+import { mount } from '@vue/test-utils'
+import SectionHeader from '../SectionHeader.vue'
+
+describe('SectionHeader', () => {
+  it('renders the section label as an h2', () => {
+    const wrapper = mount(SectionHeader, { props: { label: 'Today' } })
+    const h2 = wrapper.find('h2')
+    expect(h2.exists()).toBe(true)
+    expect(h2.text()).toBe('Today')
+  })
+
+  it('does not apply emphasized class by default', () => {
+    const wrapper = mount(SectionHeader, { props: { label: 'Later' } })
+    expect(wrapper.find('.section-header--emphasized').exists()).toBe(false)
+  })
+
+  it('applies emphasized class when emphasized prop is true', () => {
+    const wrapper = mount(SectionHeader, { props: { label: 'Today', emphasized: true } })
+    expect(wrapper.find('.section-header--emphasized').exists()).toBe(true)
+  })
+
+  it('does not apply emphasized class when emphasized prop is false', () => {
+    const wrapper = mount(SectionHeader, { props: { label: 'Past', emphasized: false } })
+    expect(wrapper.find('.section-header--emphasized').exists()).toBe(false)
+  })
+})

frontend/src/components/__tests__/useEventGrouping.spec.ts

@@ -0,0 +1,158 @@
+import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest'
+import { useEventGrouping } from '../../composables/useEventGrouping'
+import type { StoredEvent } from '../../composables/useEventStorage'
+
+function makeEvent(overrides: Partial<StoredEvent> & { dateTime: string }): StoredEvent {
+  return {
+    eventToken: `evt-${Math.random().toString(36).slice(2, 8)}`,
+    title: 'Test Event',
+    expiryDate: '',
+    ...overrides,
+  }
+}
+
+describe('useEventGrouping', () => {
+  // Fixed "now": Wednesday, 2026-03-11 12:00 local
+  const NOW = new Date(2026, 2, 11, 12, 0, 0)
+
+  beforeEach(() => {
+    vi.useFakeTimers()
+    vi.setSystemTime(NOW)
+  })
+
+  afterEach(() => {
+    vi.useRealTimers()
+  })
+
+  it('returns empty array when no events', () => {
+    const sections = useEventGrouping([], NOW)
+    expect(sections).toEqual([])
+  })
+
+  it('classifies a today event into "today" section', () => {
+    const event = makeEvent({ dateTime: '2026-03-11T18:30:00' })
+    const sections = useEventGrouping([event], NOW)
+    expect(sections).toHaveLength(1)
+    expect(sections[0]!.key).toBe('today')
+    expect(sections[0]!.label).toBe('Today')
+    expect(sections[0]!.dateGroups[0]!.events).toHaveLength(1)
+  })
+
+  it('classifies events into all five sections', () => {
+    const events = [
+      makeEvent({ title: 'Today', dateTime: '2026-03-11T10:00:00' }),
+      makeEvent({ title: 'This Week', dateTime: '2026-03-13T10:00:00' }), // Friday (same week)
+      makeEvent({ title: 'Next Week', dateTime: '2026-03-16T10:00:00' }), // Monday next week
+      makeEvent({ title: 'Later', dateTime: '2026-03-30T10:00:00' }), // far future
+      makeEvent({ title: 'Past', dateTime: '2026-03-09T10:00:00' }), // Monday (past)
+    ]
+    const sections = useEventGrouping(events, NOW)
+    expect(sections).toHaveLength(5)
+    expect(sections[0]!.key).toBe('today')
+    expect(sections[1]!.key).toBe('thisWeek')
+    expect(sections[2]!.key).toBe('nextWeek')
+    expect(sections[3]!.key).toBe('later')
+    expect(sections[4]!.key).toBe('past')
+  })
+
+  it('omits empty sections', () => {
+    const events = [
+      makeEvent({ title: 'Today', dateTime: '2026-03-11T10:00:00' }),
+      makeEvent({ title: 'Past', dateTime: '2026-03-01T10:00:00' }),
+    ]
+    const sections = useEventGrouping(events, NOW)
+    expect(sections).toHaveLength(2)
+    expect(sections[0]!.key).toBe('today')
+    expect(sections[1]!.key).toBe('past')
+  })
+
+  it('sorts upcoming events ascending by time', () => {
+    const events = [
+      makeEvent({ title: 'Later', dateTime: '2026-03-11T20:00:00' }),
+      makeEvent({ title: 'Earlier', dateTime: '2026-03-11T08:00:00' }),
+    ]
+    const sections = useEventGrouping(events, NOW)
+    const todayEvents = sections[0]!.dateGroups[0]!.events
+    expect(todayEvents[0]!.title).toBe('Earlier')
+    expect(todayEvents[1]!.title).toBe('Later')
+  })
+
+  it('sorts past events descending by time (most recent first)', () => {
+    const events = [
+      makeEvent({ title: 'Older', dateTime: '2026-03-01T10:00:00' }),
+      makeEvent({ title: 'Newer', dateTime: '2026-03-09T10:00:00' }),
+    ]
+    const sections = useEventGrouping(events, NOW)
+    const pastEvents = sections[0]!.dateGroups
+    expect(pastEvents[0]!.events[0]!.title).toBe('Newer')
+    expect(pastEvents[1]!.events[0]!.title).toBe('Older')
+  })
+
+  it('groups events by date within a section', () => {
+    const events = [
+      makeEvent({ title: 'Fri AM', dateTime: '2026-03-13T09:00:00' }),
+      makeEvent({ title: 'Fri PM', dateTime: '2026-03-13T18:00:00' }),
+      makeEvent({ title: 'Sat', dateTime: '2026-03-14T12:00:00' }),
+    ]
+    const sections = useEventGrouping(events, NOW)
+    expect(sections[0]!.key).toBe('thisWeek')
+    const dateGroups = sections[0]!.dateGroups
+    expect(dateGroups).toHaveLength(2) // Friday and Saturday
+    expect(dateGroups[0]!.events).toHaveLength(2) // Two Friday events
+    expect(dateGroups[1]!.events).toHaveLength(1) // One Saturday event
+  })
+
+  it('sets showSubheader=false for "today" section', () => {
+    const event = makeEvent({ dateTime: '2026-03-11T18:00:00' })
+    const sections = useEventGrouping([event], NOW)
+    expect(sections[0]!.dateGroups[0]!.showSubheader).toBe(false)
+  })
+
+  it('sets showSubheader=true for non-today sections', () => {
+    const events = [
+      makeEvent({ dateTime: '2026-03-13T10:00:00' }), // thisWeek
+      makeEvent({ dateTime: '2026-03-30T10:00:00' }), // later (beyond next week)
+      makeEvent({ dateTime: '2026-03-01T10:00:00' }), // past
+    ]
+    const sections = useEventGrouping(events, NOW)
+    for (const section of sections) {
+      for (const group of section.dateGroups) {
+        expect(group.showSubheader).toBe(true)
+      }
+    }
+  })
+
+  it('sets emphasized=true only for "today" section', () => {
+    const events = [
+      makeEvent({ dateTime: '2026-03-11T18:00:00' }),
+      makeEvent({ dateTime: '2026-03-30T10:00:00' }),
+    ]
+    const sections = useEventGrouping(events, NOW)
+    expect(sections[0]!.emphasized).toBe(true) // today
+    expect(sections[1]!.emphasized).toBe(false) // later
+  })
+
+  it('on Sunday, tomorrow (Monday) goes to "nextWeek" not "thisWeek"', () => {
+    // Sunday 2026-03-15
+    const sunday = new Date(2026, 2, 15, 12, 0, 0)
+    const mondayEvent = makeEvent({ title: 'Monday', dateTime: '2026-03-16T10:00:00' })
+    const sections = useEventGrouping([mondayEvent], sunday)
+    expect(sections).toHaveLength(1)
+    expect(sections[0]!.key).toBe('nextWeek')
+  })
+
+  it('on Sunday, today events still appear under "today"', () => {
+    const sunday = new Date(2026, 2, 15, 12, 0, 0)
+    const todayEvent = makeEvent({ dateTime: '2026-03-15T18:00:00' })
+    const sections = useEventGrouping([todayEvent], sunday)
+    expect(sections[0]!.key).toBe('today')
+  })
+
+  it('dateGroup labels are formatted via Intl', () => {
+    const event = makeEvent({ dateTime: '2026-03-13T10:00:00' }) // Friday
+    const sections = useEventGrouping([event], NOW)
+    const label = sections[0]!.dateGroups[0]!.label
+    // The exact format depends on locale, but should contain the day number
+    expect(label).toContain('13')
+  })
+})

frontend/src/composables/useEventGrouping.ts

@@ -0,0 +1,149 @@
+import type { StoredEvent } from './useEventStorage'
+
+export type SectionKey = 'today' | 'thisWeek' | 'nextWeek' | 'later' | 'past'
+
+export interface DateGroup {
+  dateKey: string
+  label: string
+  events: StoredEvent[]
+  showSubheader: boolean
+}
+
+export interface EventSection {
+  key: SectionKey
+  label: string
+  dateGroups: DateGroup[]
+  emphasized: boolean
+}
+
+const SECTION_ORDER: SectionKey[] = ['today', 'thisWeek', 'nextWeek', 'later', 'past']
+
+const SECTION_LABELS: Record<SectionKey, string> = {
+  today: 'Today',
+  thisWeek: 'This Week',
+  nextWeek: 'Next Week',
+  later: 'Later',
+  past: 'Past',
+}
+
+function startOfDay(date: Date): Date {
+  const d = new Date(date)
+  d.setHours(0, 0, 0, 0)
+  return d
+}
+
+function endOfDay(date: Date): Date {
+  const d = new Date(date)
+  d.setHours(23, 59, 59, 999)
+  return d
+}
+
+function endOfWeek(date: Date): Date {
+  const d = new Date(date)
+  const dayOfWeek = d.getDay() // 0=Sun, 1=Mon, ..., 6=Sat
+  // ISO week: Monday is first day. End of week = Sunday.
+  // If today is Sunday (0), end of week is today.
+  // Otherwise, days until Sunday = 7 - dayOfWeek
+  const daysUntilSunday = dayOfWeek === 0 ? 0 : 7 - dayOfWeek
+  d.setDate(d.getDate() + daysUntilSunday)
+  return endOfDay(d)
+}
+
+function endOfNextWeek(date: Date): Date {
+  const thisWeekEnd = endOfWeek(date)
+  const d = new Date(thisWeekEnd)
+  d.setDate(d.getDate() + 7)
+  return endOfDay(d)
+}
+
+function toDateKey(date: Date): string {
+  const y = date.getFullYear()
+  const m = String(date.getMonth() + 1).padStart(2, '0')
+  const d = String(date.getDate()).padStart(2, '0')
+  return `${y}-${m}-${d}`
+}
+
+function formatDateLabel(date: Date): string {
+  return new Intl.DateTimeFormat(undefined, {
+    weekday: 'short',
+    day: 'numeric',
+    month: 'short',
+  }).format(date)
+}
+
+function classifyEvent(eventDate: Date, todayStart: Date, todayEnd: Date, weekEnd: Date, nextWeekEnd: Date): SectionKey {
+  if (eventDate < todayStart) return 'past'
+  if (eventDate <= todayEnd) return 'today'
+  if (eventDate <= weekEnd) return 'thisWeek'
+  if (eventDate <= nextWeekEnd) return 'nextWeek'
+  return 'later'
+}
+
+export function useEventGrouping(events: StoredEvent[], now: Date = new Date()): EventSection[] {
+  const todayStart = startOfDay(now)
+  const todayEnd = endOfDay(now)
+  const weekEnd = endOfWeek(now)
+  const nextWeekEnd = endOfNextWeek(now)
+
+  // Classify events into sections
+  const buckets: Record<SectionKey, StoredEvent[]> = {
+    today: [],
+    thisWeek: [],
+    nextWeek: [],
+    later: [],
+    past: [],
+  }
+
+  for (const event of events) {
+    const eventDate = new Date(event.dateTime)
+    const section = classifyEvent(eventDate, todayStart, todayEnd, weekEnd, nextWeekEnd)
+    buckets[section].push(event)
+  }
+
+  // Build sections
+  const sections: EventSection[] = []
+
+  for (const key of SECTION_ORDER) {
+    const sectionEvents = buckets[key]
+    if (sectionEvents.length === 0) continue
+
+    // Sort events
+    const ascending = key !== 'past'
+    sectionEvents.sort((a, b) => {
+      const diff = new Date(a.dateTime).getTime() - new Date(b.dateTime).getTime()
+      return ascending ? diff : -diff
+    })
+
+    // Group by date
+    const dateGroupMap = new Map<string, StoredEvent[]>()
+    for (const event of sectionEvents) {
+      const dateKey = toDateKey(new Date(event.dateTime))
+      const group = dateGroupMap.get(dateKey)
+      if (group) {
+        group.push(event)
+      } else {
+        dateGroupMap.set(dateKey, [event])
+      }
+    }
+
+    // Convert to DateGroup array (order preserved from sorted events)
+    const dateGroups: DateGroup[] = []
+    for (const [dateKey, groupEvents] of dateGroupMap) {
+      dateGroups.push({
+        dateKey,
+        label: formatDateLabel(new Date(groupEvents[0]!.dateTime)),
+        events: groupEvents,
+        showSubheader: key !== 'today',
+      })
+    }
+
+    sections.push({
+      key,
+      label: SECTION_LABELS[key],
+      dateGroups,
+      emphasized: key === 'today',
+    })
+  }
+
+  return sections
+}