diff --git a/docs/frontend/calendar-export.md b/docs/frontend/calendar-export.md
new file mode 100644
index 00000000..d4db3395
--- /dev/null
+++ b/docs/frontend/calendar-export.md
@@ -0,0 +1,55 @@
+# Calendar export (#65)
+
+The project detail page exposes an **Add to Calendar** button that downloads an
+`.ics` file containing the project's deadlines so they can be added to Google,
+Apple or Outlook calendars.
+
+## Pieces
+
+| Module | Responsibility |
+|--------|----------------|
+| `frontend/lib/generateICS.ts` | RFC 5545 serialisation: escaping, line folding, all-day/timed events, `downloadICS` |
+| `frontend/lib/project-calendar.ts` | Turns a project into events: milestone due dates plus the project deadline, with stable UIDs |
+
+Both the default and localized project pages call
+`buildProjectCalendarEvents`, so the two routes no longer drift (they previously
+emitted different `UID`s and descriptions for the same milestone, and only one of
+them requested all-day events — a flag the generator used to ignore).
+
+## What gets exported
+
+- **One event per milestone due date** — `UID`
+  `agenticpay-project-<projectId>-milestone-<milestoneId>@agenticpay`.
+- **One event for the project deadline** — `UID`
+  `agenticpay-project-<projectId>-deadline@agenticpay`. It is skipped when a
+  milestone already falls on that same UTC day, because the contract currently
+  maps the project deadline onto a single milestone and duplicating it would
+  clutter the calendar.
+
+UIDs are stable across exports, so re-importing updates existing entries instead
+of creating duplicates.
+
+## RFC 5545 details
+
+- **TEXT escaping (§3.3.11).** `\`, `;`, `,` and newlines in
+  `SUMMARY`/`DESCRIPTION`/`LOCATION` are escaped. Without this a title such as
+  `Redesign, phase 2` is truncated by most clients.
+- **Line folding (§3.1).** Content lines longer than 75 octets are folded with
+  CRLF + a single space, and multi-byte UTF-8 characters are never split.
+- **All-day events.** Due dates are dates, not instants, so they are emitted as
+  `DTSTART;VALUE=DATE:YYYYMMDD` with an **exclusive** `DTEND` on the following
+  day. Pass `allDay: false` for timed events (default duration one hour).
+- **Invalid input is skipped.** Events with missing/unparseable dates, UIDs or
+  summaries are dropped rather than emitting `NaN` fields, which would make the
+  entire calendar unparseable.
+- **CRLF line endings**, `VERSION:2.0`, `CALSCALE:GREGORIAN`, `METHOD:PUBLISH`
+  and a `PRODID`.
+
+## Tests
+
+`frontend/lib/__tests__/generateICS.test.ts` covers escaping, folding,
+all-day/timed rendering, invalid input and the envelope.
+
+`frontend/lib/__tests__/project-calendar.test.ts` covers event building, the
+deadline milestone deduplication rule, filenames and the end-to-end
+project-to-`.ics` path (including titles containing commas).
diff --git a/frontend/app/[locale]/dashboard/projects/[id]/page.tsx b/frontend/app/[locale]/dashboard/projects/[id]/page.tsx
index beec73eb..d6bdc0d2 100644
--- a/frontend/app/[locale]/dashboard/projects/[id]/page.tsx
+++ b/frontend/app/[locale]/dashboard/projects/[id]/page.tsx
@@ -23,6 +23,7 @@ import { MarkdownContent } from '@/components/markdown/MarkdownContent';
 import { CopyButton } from '@/components/ui/copy-button';
 import { parseEther } from 'viem';
 import { generateICS, downloadICS } from '@/lib/generateICS';
+import { buildProjectCalendarEvents, buildProjectCalendarFilename } from '@/lib/project-calendar';
 import { CommentThread } from '@/components/collaboration/CommentThread';
 import { ActivityFeed } from '@/components/collaboration/ActivityFeed';
 
@@ -118,29 +119,23 @@ export default function ProjectDetailPage() {
   };
 
   const handleAddToCalendar = () => {
-    const events = project.milestones
-      .filter((m) => m.dueDate)
-      .map((m) => ({
-        uid: `agenticpay-project-${project.id}-milestone-${m.id}@agenticpay`,
-        summary: `${project.title} — ${m.title}`,
-        description: [
-          m.description,
-          `Project: ${project.title}`,
-          `Amount: ${m.amount} ${project.currency}`,
-          `Status: ${m.status}`,
-          project.githubRepo ? `Repository: ${project.githubRepo}` : undefined,
-        ].filter(Boolean).join('\n'),
-        start: new Date(m.dueDate!),
-        allDay: true,
-      }));
+    // Shared with the default page so both export identical, RFC 5545-correct
+    // calendars covering milestone dates and the project deadline (issue #65).
+    const events = buildProjectCalendarEvents({
+      projectId: project.id,
+      projectTitle: project.title,
+      currency: project.currency,
+      githubRepo: project.githubRepo,
+      deadline: project.deadline,
+      milestones: project.milestones,
+    });
 
     if (events.length === 0) {
-      toast.info('No milestone due dates to export.');
+      toast.info('No project or milestone dates to export.');
       return;
     }
 
-    const filename = `${project.title.trim().replace(/\s+/g, '-') || `project-${project.id}`}-milestones.ics`;
-    downloadICS(filename, generateICS(events));
+    downloadICS(buildProjectCalendarFilename(project.title), generateICS(events));
     toast.success('Calendar file downloaded.');
   };
 
diff --git a/frontend/app/dashboard/projects/[id]/page.tsx b/frontend/app/dashboard/projects/[id]/page.tsx
index c2fd7a7e..194d41c2 100644
--- a/frontend/app/dashboard/projects/[id]/page.tsx
+++ b/frontend/app/dashboard/projects/[id]/page.tsx
@@ -23,6 +23,7 @@ import { MarkdownContent } from '@/components/markdown/MarkdownContent';
 import { CopyButton } from '@/components/ui/copy-button';
 import { parseEther } from 'viem';
 import { generateICS, downloadICS } from '@/lib/generateICS';
+import { buildProjectCalendarEvents, buildProjectCalendarFilename } from '@/lib/project-calendar';
 
 type PendingTransaction = {
   functionName: string;
@@ -115,21 +116,24 @@ export default function ProjectDetailPage() {
   };
 
   const handleAddToCalendar = () => {
-    const events = project.milestones
-      .filter((m) => m.dueDate)
-      .map((m) => ({
-        uid: `milestone-${m.id}@agenticpay`,
-        summary: `${project.title} — ${m.title}`,
-        description: m.description ?? undefined,
-        start: new Date(m.dueDate!),
-      }));
+    // Shared with the localized page so both export identical, RFC 5545-correct
+    // calendars covering milestone dates and the project deadline (issue #65).
+    const events = buildProjectCalendarEvents({
+      projectId: project.id,
+      projectTitle: project.title,
+      currency: project.currency,
+      githubRepo: project.githubRepo,
+      deadline: project.deadline,
+      milestones: project.milestones,
+    });
 
     if (events.length === 0) {
-      toast.info('No milestone due dates to export.');
+      toast.info('No project or milestone dates to export.');
       return;
     }
 
-    downloadICS(`${project.title.replace(/\s+/g, '-')}.ics`, generateICS(events));
+    downloadICS(buildProjectCalendarFilename(project.title), generateICS(events));
+    toast.success('Calendar file downloaded.');
   };
 
   return (
diff --git a/frontend/lib/__tests__/generateICS.test.ts b/frontend/lib/__tests__/generateICS.test.ts
new file mode 100644
index 00000000..37343644
--- /dev/null
+++ b/frontend/lib/__tests__/generateICS.test.ts
@@ -0,0 +1,224 @@
+/**
+ * generateICS tests — Issue #65
+ */
+import { describe, expect, it } from 'vitest';
+
+import {
+  escapeICSText,
+  foldICSLine,
+  formatICSDate,
+  formatICSDateTime,
+  generateICS,
+  isValidDate,
+  type ICSEvent,
+} from '@/lib/generateICS';
+
+const NOW = new Date('2026-03-01T09:30:00Z');
+
+function event(overrides: Partial<ICSEvent> = {}): ICSEvent {
+  return {
+    uid: 'agenticpay-project-1-milestone-1@agenticpay',
+    summary: 'Website redesign',
+    start: new Date('2026-04-15T00:00:00Z'),
+    ...overrides,
+  };
+}
+
+describe('escapeICSText', () => {
+  it('escapes commas so a summary is not truncated', () => {
+    expect(escapeICSText('Redesign, phase 2')).toBe('Redesign\\, phase 2');
+  });
+
+  it('escapes semicolons and backslashes', () => {
+    expect(escapeICSText('a;b\\c')).toBe('a\\;b\\\\c');
+  });
+
+  it('converts newlines to the \\n escape', () => {
+    expect(escapeICSText('line one\nline two\r\nline three')).toBe('line one\\nline two\\nline three');
+  });
+});
+
+describe('date formatting', () => {
+  it('formats a UTC date as YYYYMMDD with zero padding', () => {
+    expect(formatICSDate(new Date('2026-01-05T23:00:00Z'))).toBe('20260105');
+  });
+
+  it('formats a UTC date-time as YYYYMMDDTHHMMSSZ', () => {
+    expect(formatICSDateTime(new Date('2026-01-05T04:07:09Z'))).toBe('20260105T040709Z');
+  });
+
+  it('recognises invalid dates', () => {
+    expect(isValidDate(new Date('nope'))).toBe(false);
+    expect(isValidDate(new Date('2026-01-05T00:00:00Z'))).toBe(true);
+    expect(isValidDate(undefined)).toBe(false);
+  });
+});
+
+describe('foldICSLine', () => {
+  it('leaves short lines untouched', () => {
+    expect(foldICSLine('SUMMARY:short')).toBe('SUMMARY:short');
+  });
+
+  it('folds long lines with CRLF plus a leading space', () => {
+    const line = `DESCRIPTION:${'x'.repeat(200)}`;
+    const folded = foldICSLine(line);
+
+    expect(folded).toContain('\r\n ');
+    for (const segment of folded.split('\r\n')) {
+      expect(new TextEncoder().encode(segment).length).toBeLessThanOrEqual(75);
+    }
+  });
+
+  it('round-trips when unfolded by a parser', () => {
+    const line = `DESCRIPTION:${'y'.repeat(300)}`;
+    const unfolded = foldICSLine(line).replace(/\r\n /g, '');
+
+    expect(unfolded).toBe(line);
+  });
+
+  it('never splits a multi-byte character', () => {
+    const line = `SUMMARY:${'é'.repeat(120)}`;
+    const folded = foldICSLine(line);
+
+    for (const segment of folded.split('\r\n')) {
+      expect(segment).not.toContain('\uFFFD');
+      expect(new TextEncoder().encode(segment).length).toBeLessThanOrEqual(75);
+    }
+    expect(folded.replace(/\r\n /g, '')).toBe(line);
+  });
+});
+
+describe('generateICS', () => {
+  it('emits a VCALENDAR envelope with the required properties', () => {
+    const ics = generateICS([event()], NOW);
+    const lines = ics.split('\r\n');
+
+    expect(lines[0]).toBe('BEGIN:VCALENDAR');
+    expect(lines).toContain('VERSION:2.0');
+    expect(lines).toContain('CALSCALE:GREGORIAN');
+    expect(lines).toContain('PRODID:-//AgenticPay//Calendar Export//EN');
+    expect(lines.at(-1)).toBe('END:VCALENDAR');
+  });
+
+  it('uses CRLF line endings', () => {
+    const ics = generateICS([event()], NOW);
+    const lines = ics.split('\n');
+
+    expect(ics).toContain('\r\n');
+    // Every line but the last is terminated by CRLF.
+    expect(lines.slice(0, -1).every((line) => line.endsWith('\r'))).toBe(true);
+    expect(lines.at(-1)).not.toContain('\r');
+  });
+
+  it('renders an all-day event with an exclusive DTEND', () => {
+    const ics = generateICS([event({ start: new Date('2026-04-15T00:00:00Z') })], NOW);
+
+    expect(ics).toContain('DTSTART;VALUE=DATE:20260415');
+    expect(ics).toContain('DTEND;VALUE=DATE:20260416');
+    expect(ics).not.toContain('DTSTART:2026');
+  });
+
+  it('respects an explicit end date for all-day events', () => {
+    const ics = generateICS(
+      [event({ start: new Date('2026-04-15T00:00:00Z'), end: new Date('2026-04-18T00:00:00Z') })],
+      NOW
+    );
+
+    expect(ics).toContain('DTEND;VALUE=DATE:20260418');
+  });
+
+  it('renders a timed event when allDay is false', () => {
+    const ics = generateICS(
+      [
+        event({
+          allDay: false,
+          start: new Date('2026-04-15T13:00:00Z'),
+          end: new Date('2026-04-15T14:30:00Z'),
+        }),
+      ],
+      NOW
+    );
+
+    expect(ics).toContain('DTSTART:20260415T130000Z');
+    expect(ics).toContain('DTEND:20260415T143000Z');
+  });
+
+  it('defaults a timed event to one hour when no end is given', () => {
+    const ics = generateICS([event({ allDay: false, start: new Date('2026-04-15T13:00:00Z') })], NOW);
+
+    expect(ics).toContain('DTEND:20260415T140000Z');
+  });
+
+  it('defaults to an all-day event when allDay is omitted', () => {
+    const ics = generateICS([event()], NOW);
+    expect(ics).toContain('DTSTART;VALUE=DATE');
+  });
+
+  it('escapes the summary and description', () => {
+    const ics = generateICS(
+      [event({ summary: 'Redesign, phase 2', description: 'Line one\nLine two; done, maybe' })],
+      NOW
+    );
+
+    expect(ics).toContain('SUMMARY:Redesign\\, phase 2');
+    expect(ics).toContain('Line one\\nLine two\\; done\\, maybe');
+  });
+
+  it('stamps DTSTAMP from the provided clock', () => {
+    expect(generateICS([event()], NOW)).toContain('DTSTAMP:20260301T093000Z');
+  });
+
+  it('keeps the UID stable so re-imports update instead of duplicating', () => {
+    const ics = generateICS([event()], NOW);
+    expect(ics).toContain('UID:agenticpay-project-1-milestone-1@agenticpay');
+  });
+
+  it('includes the location when provided', () => {
+    expect(generateICS([event({ location: 'Remote' })], NOW)).toContain('LOCATION:Remote');
+  });
+
+  it('skips events with an invalid start date', () => {
+    const ics = generateICS([event({ start: new Date('not-a-date') })], NOW);
+
+    expect(ics).not.toContain('BEGIN:VEVENT');
+    expect(ics).not.toContain('NaN');
+  });
+
+  it('skips events without a uid or summary', () => {
+    const ics = generateICS([event({ uid: '' }), event({ summary: '' })], NOW);
+    expect(ics).not.toContain('BEGIN:VEVENT');
+  });
+
+  it('keeps valid events when another event is invalid', () => {
+    const ics = generateICS(
+      [event({ start: new Date('bad') }), event({ uid: 'ok-1', summary: 'Good' })],
+      NOW
+    );
+
+    const blocks = ics.split('BEGIN:VEVENT').length - 1;
+    expect(blocks).toBe(1);
+    expect(ics).toContain('SUMMARY:Good');
+  });
+
+  it('returns a valid empty calendar for no events', () => {
+    const ics = generateICS([], NOW);
+    expect(ics).toBe(
+      [
+        'BEGIN:VCALENDAR',
+        'VERSION:2.0',
+        'PRODID:-//AgenticPay//Calendar Export//EN',
+        'CALSCALE:GREGORIAN',
+        'METHOD:PUBLISH',
+        'X-WR-CALNAME:AgenticPay',
+        'END:VCALENDAR',
+      ].join('\r\n')
+    );
+  });
+
+  it('folds a very long description across multiple lines', () => {
+    const ics = generateICS([event({ description: 'z'.repeat(400) })], NOW);
+
+    expect(ics).toContain('\r\n ');
+    expect(ics.replace(/\r\n /g, '')).toContain('z'.repeat(400));
+  });
+});
diff --git a/frontend/lib/__tests__/project-calendar.test.ts b/frontend/lib/__tests__/project-calendar.test.ts
new file mode 100644
index 00000000..91a5db82
--- /dev/null
+++ b/frontend/lib/__tests__/project-calendar.test.ts
@@ -0,0 +1,226 @@
+/**
+ * buildProjectCalendarEvents tests — Issue #65
+ */
+import { describe, expect, it } from 'vitest';
+
+import { generateICS } from '@/lib/generateICS';
+import {
+  buildProjectCalendarEvents,
+  buildProjectCalendarFilename,
+  type CalendarMilestone,
+} from '@/lib/project-calendar';
+
+const DUE = '2026-04-15T00:00:00.000Z';
+
+function milestone(overrides: Partial<CalendarMilestone> = {}): CalendarMilestone {
+  return {
+    id: '1',
+    title: 'Project Deliverable',
+    description: 'Build the thing',
+    amount: '1.5',
+    status: 'pending',
+    dueDate: DUE,
+    ...overrides,
+  };
+}
+
+describe('buildProjectCalendarEvents — milestone dates', () => {
+  it('creates one event per milestone with a due date', () => {
+    const events = buildProjectCalendarEvents({
+      projectId: '7',
+      projectTitle: 'Redesign',
+      currency: 'ETH',
+      milestones: [milestone()],
+    });
+
+    expect(events).toHaveLength(1);
+    expect(events[0]!.uid).toBe('agenticpay-project-7-milestone-1@agenticpay');
+    expect(events[0]!.summary).toBe('Redesign — Project Deliverable');
+    expect(events[0]!.start.toISOString()).toBe(DUE);
+    expect(events[0]!.allDay).toBe(true);
+  });
+
+  it('includes amount, status, description and repository in the details', () => {
+    const events = buildProjectCalendarEvents({
+      projectId: '7',
+      projectTitle: 'Redesign',
+      currency: 'ETH',
+      githubRepo: 'https://github.com/a/b',
+      milestones: [milestone()],
+    });
+
+    const description = events[0]!.description ?? '';
+    expect(description).toContain('Build the thing');
+    expect(description).toContain('Project: Redesign');
+    expect(description).toContain('Amount: 1.5 ETH');
+    expect(description).toContain('Status: pending');
+    expect(description).toContain('Repository: https://github.com/a/b');
+  });
+
+  it('omits the currency when it is unknown', () => {
+    const events = buildProjectCalendarEvents({
+      projectId: '7',
+      projectTitle: 'Redesign',
+      milestones: [milestone()],
+    });
+
+    expect(events[0]!.description).toContain('Amount: 1.5');
+    expect(events[0]!.description).not.toContain('Amount: 1.5 ');
+  });
+
+  it('includes multiple milestone dates', () => {
+    const events = buildProjectCalendarEvents({
+      projectId: '7',
+      projectTitle: 'Redesign',
+      milestones: [
+        milestone({ id: '1', title: 'Design', dueDate: '2026-04-01T00:00:00.000Z' }),
+        milestone({ id: '2', title: 'Build', dueDate: '2026-05-01T00:00:00.000Z' }),
+      ],
+    });
+
+    expect(events).toHaveLength(2);
+    expect(events.map((e) => e.summary)).toEqual([
+      'Redesign — Design',
+      'Redesign — Build',
+    ]);
+  });
+
+  it('skips milestones without a due date', () => {
+    const events = buildProjectCalendarEvents({
+      projectId: '7',
+      projectTitle: 'Redesign',
+      milestones: [milestone({ dueDate: undefined })],
+    });
+
+    expect(events).toEqual([]);
+  });
+
+  it('skips milestones with an unparseable due date', () => {
+    const events = buildProjectCalendarEvents({
+      projectId: '7',
+      projectTitle: 'Redesign',
+      milestones: [milestone({ dueDate: 'not-a-date' })],
+    });
+
+    expect(events).toEqual([]);
+  });
+
+  it('ignores duplicate milestone identifiers', () => {
+    const events = buildProjectCalendarEvents({
+      projectId: '7',
+      projectTitle: 'Redesign',
+      milestones: [milestone(), milestone()],
+    });
+
+    expect(events).toHaveLength(1);
+  });
+});
+
+describe('buildProjectCalendarEvents — project deadline', () => {
+  it('adds a deadline event when no milestone falls on that day', () => {
+    const events = buildProjectCalendarEvents({
+      projectId: '7',
+      projectTitle: 'Redesign',
+      deadline: '2026-06-30T00:00:00.000Z',
+      milestones: [milestone({ dueDate: '2026-04-15T00:00:00.000Z' })],
+    });
+
+    expect(events).toHaveLength(2);
+    const deadline = events.find((e) => e.uid === 'agenticpay-project-7-deadline@agenticpay')!;
+    expect(deadline.summary).toBe('Redesign — project deadline');
+    expect(deadline.start.toISOString()).toBe('2026-06-30T00:00:00.000Z');
+  });
+
+  it('does not duplicate the deadline when a milestone covers the same day', () => {
+    const events = buildProjectCalendarEvents({
+      projectId: '7',
+      projectTitle: 'Redesign',
+      deadline: DUE,
+      milestones: [milestone()],
+    });
+
+    expect(events).toHaveLength(1);
+    expect(events.some((e) => e.uid.includes('deadline'))).toBe(false);
+  });
+
+  it('still adds the deadline when a milestone is on a different time of the same day', () => {
+    const events = buildProjectCalendarEvents({
+      projectId: '7',
+      projectTitle: 'Redesign',
+      deadline: '2026-04-15T18:00:00.000Z',
+      milestones: [milestone({ dueDate: DUE })],
+    });
+
+    // Same UTC day, so the milestone already represents it.
+    expect(events).toHaveLength(1);
+  });
+
+  it('can be told to skip the deadline event', () => {
+    const events = buildProjectCalendarEvents({
+      projectId: '7',
+      projectTitle: 'Redesign',
+      deadline: '2026-06-30T00:00:00.000Z',
+      milestones: [milestone()],
+      includeDeadline: false,
+    });
+
+    expect(events).toHaveLength(1);
+  });
+
+  it('skips an invalid deadline', () => {
+    const events = buildProjectCalendarEvents({
+      projectId: '7',
+      projectTitle: 'Redesign',
+      deadline: 'not-a-date',
+      milestones: [milestone({ dueDate: '2026-04-15T00:00:00.000Z' })],
+    });
+
+    expect(events).toHaveLength(1);
+  });
+
+  it('handles a project with only a deadline', () => {
+    const events = buildProjectCalendarEvents({
+      projectId: '7',
+      projectTitle: 'Redesign',
+      deadline: '2026-06-30T00:00:00.000Z',
+      milestones: [],
+    });
+
+    expect(events).toHaveLength(1);
+    expect(events[0]!.uid).toBe('agenticpay-project-7-deadline@agenticpay');
+  });
+});
+
+describe('buildProjectCalendarEvents → generateICS', () => {
+  it('produces an importable calendar for milestone and deadline dates', () => {
+    const events = buildProjectCalendarEvents({
+      projectId: '7',
+      projectTitle: 'Redesign, phase 2',
+      currency: 'ETH',
+      deadline: '2026-06-30T00:00:00.000Z',
+      milestones: [milestone({ title: 'Design, round 1' })],
+    });
+
+    const ics = generateICS(events, new Date('2026-03-01T00:00:00Z'));
+
+    expect(ics.split('BEGIN:VEVENT').length - 1).toBe(2);
+    // Commas in user content are escaped, so the calendar stays parseable.
+    expect(ics).toContain('SUMMARY:Redesign\\, phase 2 — Design\\, round 1');
+    expect(ics).toContain('DTSTART;VALUE=DATE:20260415');
+    expect(ics).toContain('DTSTART;VALUE=DATE:20260630');
+  });
+});
+
+describe('buildProjectCalendarFilename', () => {
+  it('slugifies the project title', () => {
+    expect(buildProjectCalendarFilename('Website Redesign')).toBe('Website-Redesign.ics');
+  });
+
+  it('strips characters that are unsafe in filenames', () => {
+    expect(buildProjectCalendarFilename('Redesign: phase 2 / v3?')).toBe('Redesign-phase-2-v3.ics');
+  });
+
+  it('falls back when the title slugifies to nothing', () => {
+    expect(buildProjectCalendarFilename('///')).toBe('project.ics');
+  });
+});
diff --git a/frontend/lib/generateICS.ts b/frontend/lib/generateICS.ts
index 67df975c..0dc9e309 100644
--- a/frontend/lib/generateICS.ts
+++ b/frontend/lib/generateICS.ts
@@ -1,48 +1,182 @@
-interface ICSEvent {
+/**
+ * iCalendar (`.ics`) generation — Issue #65
+ *
+ * Produces RFC 5545 calendars for project deadlines and milestone due dates so
+ * they can be added to Google/Apple/Outlook calendars.
+ *
+ * Conformance details that matter in practice:
+ *
+ * - **TEXT escaping (§3.3.11)** — backslashes, semicolons, commas and newlines
+ *   must be escaped inside `SUMMARY`/`DESCRIPTION`/`LOCATION`. A title such as
+ *   `Redesign, phase 2` otherwise truncates the field in most clients.
+ * - **Line folding (§3.1)** — lines longer than 75 octets must be folded with
+ *   CRLF + a single space, without splitting a UTF-8 sequence.
+ * - **All-day events** — due dates are dates, not instants, so they are emitted
+ *   as `DTSTART;VALUE=DATE:YYYYMMDD` with an **exclusive** `DTEND` on the
+ *   following day. Previously an `allDay` flag was accepted by callers but
+ *   silently ignored by the generator.
+ * - Invalid dates are skipped rather than emitted as `NaNundefinedZ`, which
+ *   makes the whole calendar unparseable.
+ */
+
+export interface ICSEvent {
+  /** Globally unique identifier; stable so re-imports update instead of duplicate. */
   uid: string;
   summary: string;
   description?: string;
+  location?: string;
   start: Date;
+  /** Only used for timed events; ignored when `allDay` is true. */
   end?: Date;
+  /** Emit a date-only event. Defaults to `true`, since these are due dates. */
+  allDay?: boolean;
+}
+
+/** Maximum octets per content line before folding (RFC 5545 §3.1). */
+const MAX_LINE_OCTETS = 75;
+
+const uidDomain = 'agenticpay';
+
+/** Escape a value for use in an iCalendar TEXT property (RFC 5545 §3.3.11). */
+export function escapeICSText(value: string): string {
+  return value
+    .replace(/\\/g, '\\\\')
+    .replace(/;/g, '\\;')
+    .replace(/,/g, '\\,')
+    .replace(/\r\n|\r|\n/g, '\\n');
+}
+
+function pad(value: number): string {
+  return String(value).padStart(2, '0');
+}
+
+/** `YYYYMMDD` in UTC — used for `VALUE=DATE` properties. */
+export function formatICSDate(date: Date): string {
+  return `${date.getUTCFullYear()}${pad(date.getUTCMonth() + 1)}${pad(date.getUTCDate())}`;
+}
+
+/** `YYYYMMDDTHHMMSSZ` in UTC — used for date-time properties. */
+export function formatICSDateTime(date: Date): string {
+  return (
+    `${formatICSDate(date)}T` +
+    `${pad(date.getUTCHours())}${pad(date.getUTCMinutes())}${pad(date.getUTCSeconds())}Z`
+  );
+}
+
+/** True when the value is a usable calendar date. */
+export function isValidDate(value: unknown): value is Date {
+  return value instanceof Date && !Number.isNaN(value.getTime());
+}
+
+/**
+ * Fold a content line at 75 octets, continuing with a leading space. Multi-byte
+ * UTF-8 characters are never split across a fold.
+ */
+export function foldICSLine(line: string): string {
+  const encoder = new TextEncoder();
+  if (encoder.encode(line).length <= MAX_LINE_OCTETS) return line;
+
+  const folded: string[] = [];
+  let current = '';
+  let currentOctets = 0;
+  // Continuation lines start with a space, leaving 74 octets for content.
+  let limit = MAX_LINE_OCTETS;
+
+  for (const character of line) {
+    const octets = encoder.encode(character).length;
+    if (currentOctets + octets > limit) {
+      folded.push(current);
+      current = '';
+      currentOctets = 0;
+      limit = MAX_LINE_OCTETS - 1;
+      current = ' ';
+      currentOctets = 1;
+    }
+    current += character;
+    currentOctets += octets;
+  }
+
+  if (current) folded.push(current);
+  return folded.join('\r\n');
 }
 
-function formatICSDate(date: Date): string {
-  return date.toISOString().replace(/[-:]/g, '').split('.')[0] + 'Z';
+/** Serialize a single event block. Returns `undefined` for unusable events. */
+function serializeEvent(event: ICSEvent, now: Date): string[] | undefined {
+  if (!event.uid || !event.summary || !isValidDate(event.start)) return undefined;
+
+  const allDay = event.allDay ?? true;
+  const lines = ['BEGIN:VEVENT', `UID:${escapeICSText(event.uid)}`];
+
+  lines.push(`DTSTAMP:${formatICSDateTime(now)}`);
+
+  if (allDay) {
+    // DTEND is exclusive: the day after the due date.
+    const endDate = isValidDate(event.end)
+      ? event.end
+      : new Date(event.start.getTime() + 24 * 60 * 60 * 1000);
+    lines.push(`DTSTART;VALUE=DATE:${formatICSDate(event.start)}`);
+    lines.push(`DTEND;VALUE=DATE:${formatICSDate(endDate)}`);
+  } else {
+    const end = isValidDate(event.end)
+      ? event.end
+      : new Date(event.start.getTime() + 60 * 60 * 1000);
+    lines.push(`DTSTART:${formatICSDateTime(event.start)}`);
+    lines.push(`DTEND:${formatICSDateTime(end)}`);
+  }
+
+  lines.push(`SUMMARY:${escapeICSText(event.summary)}`);
+  if (event.description) lines.push(`DESCRIPTION:${escapeICSText(event.description)}`);
+  if (event.location) lines.push(`LOCATION:${escapeICSText(event.location)}`);
+  lines.push('END:VEVENT');
+
+  return lines;
 }
 
-export function generateICS(events: ICSEvent[]): string {
+/**
+ * Build an `.ics` document. Events with missing or invalid dates are dropped so
+ * one bad deadline cannot corrupt the export.
+ */
+export function generateICS(events: ICSEvent[], now: Date = new Date()): string {
   const lines = [
     'BEGIN:VCALENDAR',
     'VERSION:2.0',
-    'PRODID:-//AgenticPay//Calendar Export//EN',
+    `PRODID:-//AgenticPay//Calendar Export//EN`,
     'CALSCALE:GREGORIAN',
     'METHOD:PUBLISH',
+    `X-WR-CALNAME:${escapeICSText('AgenticPay')}`,
   ];
 
   for (const event of events) {
-    const end = event.end ?? new Date(event.start.getTime() + 86400000);
-    lines.push(
-      'BEGIN:VEVENT',
-      `UID:${event.uid}`,
-      `DTSTAMP:${formatICSDate(new Date())}`,
-      `DTSTART:${formatICSDate(event.start)}`,
-      `DTEND:${formatICSDate(end)}`,
-      `SUMMARY:${event.summary}`,
-      ...(event.description ? [`DESCRIPTION:${event.description.replace(/\n/g, '\\n')}`] : []),
-      'END:VEVENT',
-    );
+    const serialized = serializeEvent(event, now);
+    if (serialized) lines.push(...serialized);
   }
 
   lines.push('END:VCALENDAR');
-  return lines.join('\r\n');
+
+  return lines.map(foldICSLine).join('\r\n');
 }
 
+/** Trigger a browser download of generated calendar content. */
 export function downloadICS(filename: string, content: string): void {
+  if (typeof document === 'undefined' || typeof URL.createObjectURL !== 'function') return;
+
   const blob = new Blob([content], { type: 'text/calendar;charset=utf-8' });
   const url = URL.createObjectURL(blob);
-  const a = document.createElement('a');
-  a.href = url;
-  a.download = filename;
-  a.click();
+  const anchor = document.createElement('a');
+  anchor.href = url;
+  anchor.download = filename.endsWith('.ics') ? filename : `${filename}.ics`;
+  anchor.click();
   URL.revokeObjectURL(url);
 }
+
+/** UID for a milestone due date, stable across exports. */
+export function milestoneEventUid(projectId: string, milestoneId: string): string {
+  return `agenticpay-project-${projectId}-milestone-${milestoneId}@${uidDomain}`;
+}
+
+/** UID for a project deadline, stable across exports. */
+export function deadlineEventUid(projectId: string): string {
+  return `agenticpay-project-${projectId}-deadline@${uidDomain}`;
+}
+
+export default generateICS;
diff --git a/frontend/lib/hooks/useAgenticPay.ts b/frontend/lib/hooks/useAgenticPay.ts
index da68d3a4..68706934 100644
--- a/frontend/lib/hooks/useAgenticPay.ts
+++ b/frontend/lib/hooks/useAgenticPay.ts
@@ -260,6 +260,7 @@ const formatProjectData = (data: RawProjectData): Project => {
         rawDepositedAmount: data.depositedAmount,
         rawStatus: Number(data.status),
         createdAt: new Date(Number(data.createdAt) * 1000).toISOString(),
+        deadline: new Date(Number(data.deadline) * 1000).toISOString(),
         githubRepo: data.githubRepo,
         invoiceUri: data.invoiceUri, // Pass invoiceUri
         milestones: milestones,
diff --git a/frontend/lib/project-calendar.ts b/frontend/lib/project-calendar.ts
new file mode 100644
index 00000000..6d046ac6
--- /dev/null
+++ b/frontend/lib/project-calendar.ts
@@ -0,0 +1,130 @@
+/**
+ * Project → calendar events — Issue #65
+ *
+ * Both project detail pages (default and localized) previously built their own
+ * event lists, which drifted: they used different `UID`s for the same milestone,
+ * different descriptions, and only one of them asked for all-day events. This
+ * module is the single source for the export, and it covers both acceptance
+ * criteria — **project deadlines** and **milestone dates** — without producing
+ * duplicate entries, because the contract currently maps the project deadline
+ * onto a single milestone.
+ */
+
+import {
+  deadlineEventUid,
+  isValidDate,
+  milestoneEventUid,
+  type ICSEvent,
+} from '@/lib/generateICS';
+import type { Milestone } from '@/lib/types';
+
+/** The subset of a milestone the calendar needs. */
+export type CalendarMilestone = Pick<
+  Milestone,
+  'id' | 'title' | 'description' | 'amount' | 'status' | 'dueDate'
+>;
+
+export interface ProjectCalendarInput {
+  projectId: string;
+  projectTitle: string;
+  currency?: string;
+  githubRepo?: string;
+  /** Project-level deadline (ISO 8601). */
+  deadline?: string | null;
+  milestones: CalendarMilestone[];
+  /** Include the project deadline event. Defaults to `true`. */
+  includeDeadline?: boolean;
+}
+
+function toDate(value?: string | null): Date | undefined {
+  if (!value) return undefined;
+  const date = new Date(value);
+  return isValidDate(date) ? date : undefined;
+}
+
+function sameUtcDay(a: Date, b: Date): boolean {
+  return (
+    a.getUTCFullYear() === b.getUTCFullYear() &&
+    a.getUTCMonth() === b.getUTCMonth() &&
+    a.getUTCDate() === b.getUTCDate()
+  );
+}
+
+function detailLines(input: ProjectCalendarInput, extra: Array<string | undefined>): string {
+  return [
+    ...extra,
+    `Project: ${input.projectTitle}`,
+    input.githubRepo ? `Repository: ${input.githubRepo}` : undefined,
+  ]
+    .filter((line): line is string => Boolean(line))
+    .join('\n');
+}
+
+/**
+ * Build calendar events for a project: one per milestone due date plus the
+ * project deadline itself.
+ *
+ * The deadline event is skipped when a milestone already falls on that same day
+ * (the current contract shape), so the calendar stays free of duplicates. Events
+ * with missing or unparseable dates are omitted.
+ */
+export function buildProjectCalendarEvents(input: ProjectCalendarInput): ICSEvent[] {
+  const deadline = toDate(input.deadline);
+  const events: ICSEvent[] = [];
+  const seenUids = new Set<string>();
+  const milestoneDays: Date[] = [];
+
+  for (const milestone of input.milestones) {
+    const dueDate = toDate(milestone.dueDate);
+    if (!dueDate) continue;
+
+    milestoneDays.push(dueDate);
+
+    const uid = milestoneEventUid(input.projectId, milestone.id);
+    if (seenUids.has(uid)) continue;
+    seenUids.add(uid);
+
+    events.push({
+      uid,
+      summary: `${input.projectTitle} — ${milestone.title}`,
+      description: detailLines(input, [
+        milestone.description,
+        input.currency ? `Amount: ${milestone.amount} ${input.currency}` : `Amount: ${milestone.amount}`,
+        `Status: ${milestone.status}`,
+      ]),
+      start: dueDate,
+      allDay: true,
+    });
+  }
+
+  const deadlineCoveredByMilestone =
+    deadline !== undefined && milestoneDays.some((day) => sameUtcDay(day, deadline));
+
+  if (deadline && input.includeDeadline !== false && !deadlineCoveredByMilestone) {
+    const uid = deadlineEventUid(input.projectId);
+    if (!seenUids.has(uid)) {
+      events.push({
+        uid,
+        summary: `${input.projectTitle} — project deadline`,
+        description: detailLines(input, [`Deadline: ${deadline.toISOString().slice(0, 10)}`]),
+        start: deadline,
+        allDay: true,
+      });
+    }
+  }
+
+  return events;
+}
+
+/** Filesystem-safe `.ics` filename for a project. */
+export function buildProjectCalendarFilename(projectTitle: string): string {
+  const slug = projectTitle
+    .trim()
+    .replace(/[^\w.-]+/g, '-')
+    .replace(/^-+|-+$/g, '')
+    .slice(0, 80);
+
+  return `${slug || 'project'}.ics`;
+}
+
+export default buildProjectCalendarEvents;
diff --git a/frontend/lib/types.ts b/frontend/lib/types.ts
index 46de9c9a..5da9cd9b 100644
--- a/frontend/lib/types.ts
+++ b/frontend/lib/types.ts
@@ -30,6 +30,8 @@ export interface Project {
   rawStatus?: number; // Enum index
   milestones: Milestone[];
   createdAt: string;
+  /** ISO 8601 project deadline as stored on-chain (issue #65). */
+  deadline?: string;
   githubRepo?: string;
   invoiceUri?: string; // Added invoiceUri
 }