emails

listify-api/.env.docker.example

@@ -29,3 +29,5 @@ SMTP_USER=
 SMTP_PASSWORD=
 MAIL_FROM=no-reply@listify.local
 MAIL_FROM_NAME=Listify
+
+LIST_REMINDER_POLL_INTERVAL_MS=60000

listify-api/.env.example

@@ -26,3 +26,5 @@ SMTP_USER=
 SMTP_PASSWORD=
 MAIL_FROM=no-reply@listify.local
 MAIL_FROM_NAME=Listify
+
+LIST_REMINDER_POLL_INTERVAL_MS=60000

listify-api/src/database/migrations/1781400000000-AddListReminderAt.ts

@@ -0,0 +1,21 @@
+import { MigrationInterface, QueryRunner } from 'typeorm';
+
+export class AddListReminderAt1781400000000 implements MigrationInterface {
+  name = 'AddListReminderAt1781400000000';
+
+  public async up(queryRunner: QueryRunner): Promise<void> {
+    await queryRunner.query(
+      'ALTER TABLE `user_lists` ADD `reminderAt` datetime(3) NULL',
+    );
+    await queryRunner.query(
+      'CREATE INDEX `IDX_user_lists_reminder_at` ON `user_lists` (`reminderAt`)',
+    );
+  }
+
+  public async down(queryRunner: QueryRunner): Promise<void> {
+    await queryRunner.query(
+      'DROP INDEX `IDX_user_lists_reminder_at` ON `user_lists`',
+    );
+    await queryRunner.query('ALTER TABLE `user_lists` DROP COLUMN `reminderAt`');
+  }
+}

listify-api/src/list-templates/list-template.types.ts

@@ -57,6 +57,7 @@ export interface UserList {
   name: string;
   description?: string;
   kind: ListTemplateKind;
+  reminderAt?: string;
   items: UserListItem[];
   collaborators: UserListCollaborator[];
   createdAt: string;

listify-api/src/lists/dto/create-list.dto.ts

@@ -4,4 +4,5 @@ export class CreateListDto {
   name?: string;
   description?: string;
   kind?: ListTemplateKind;
+  reminderAt?: string | null;
 }

listify-api/src/lists/dto/update-list.dto.ts

@@ -4,4 +4,5 @@ export class UpdateListDto {
   name?: string;
   description?: string;
   kind?: ListTemplateKind;
+  reminderAt?: string | null;
 }

listify-api/src/lists/list-reminder.service.spec.ts

@@ -0,0 +1,149 @@
+import { Logger } from '@nestjs/common';
+import { ConfigService } from '@nestjs/config';
+import { UserEntity } from '../auth/user.entity';
+import { MailService } from '../mail/mail.service';
+import { InMemoryRepository } from '../testing/in-memory-repository';
+import { ListReminderService } from './list-reminder.service';
+import { ListsService } from './lists.service';
+import { UserListEntity } from './user-list.entity';
+
+describe('ListReminderService', () => {
+  let listsRepository: InMemoryRepository<UserListEntity>;
+  let mailService: Pick<MailService, 'sendListReminderEmail'>;
+  let listsService: Pick<ListsService, 'publishListSnapshot'>;
+  let service: ListReminderService;
+
+  beforeEach(() => {
+    listsRepository = new InMemoryRepository<UserListEntity>();
+    mailService = {
+      sendListReminderEmail: jest.fn().mockResolvedValue(undefined),
+    };
+    listsService = {
+      publishListSnapshot: jest.fn().mockResolvedValue(undefined),
+    };
+    service = new ListReminderService(
+      listsRepository as never,
+      new ConfigService({ CLIENT_URL: 'http://client.test' }),
+      mailService as MailService,
+      listsService as ListsService,
+    );
+  });
+
+  afterEach(() => {
+    jest.restoreAllMocks();
+  });
+
+  it('sends due reminders for open items and clears the reminder', async () => {
+    const list = await saveList({
+      reminderAt: new Date('2026-06-17T08:00:00.000Z'),
+      items: [
+        { title: 'Offen', checked: false, position: 0 },
+        { title: 'Erledigt', checked: true, position: 1 },
+      ],
+    });
+
+    await service.processDueReminders(new Date('2026-06-17T09:00:00.000Z'));
+
+    expect(mailService.sendListReminderEmail).toHaveBeenCalledWith(
+      'owner@example.com',
+      {
+        listId: list.id,
+        listName: 'Testliste',
+        listUrl: `http://client.test/lists/${list.id}`,
+        openItems: [
+          {
+            title: 'Offen',
+            notes: undefined,
+            quantity: undefined,
+          },
+        ],
+      },
+    );
+    expect((await listsRepository.findOne({ where: { id: list.id } }))?.reminderAt)
+      .toBeNull();
+    expect(listsService.publishListSnapshot).toHaveBeenCalledWith(list.id);
+  });
+
+  it('clears due reminders without sending when all items are done', async () => {
+    const list = await saveList({
+      reminderAt: new Date('2026-06-17T08:00:00.000Z'),
+      items: [{ title: 'Fertig', checked: true, position: 0 }],
+    });
+
+    await service.processDueReminders(new Date('2026-06-17T09:00:00.000Z'));
+
+    expect(mailService.sendListReminderEmail).not.toHaveBeenCalled();
+    expect((await listsRepository.findOne({ where: { id: list.id } }))?.reminderAt)
+      .toBeNull();
+  });
+
+  it('keeps the reminder when sending fails', async () => {
+    jest.spyOn(Logger.prototype, 'error').mockImplementation(() => undefined);
+    jest
+      .mocked(mailService.sendListReminderEmail)
+      .mockRejectedValueOnce(new Error('smtp down'));
+    const reminderAt = new Date('2026-06-17T08:00:00.000Z');
+    const list = await saveList({
+      reminderAt,
+      items: [{ title: 'Offen', checked: false, position: 0 }],
+    });
+
+    await service.processDueReminders(new Date('2026-06-17T09:00:00.000Z'));
+
+    expect((await listsRepository.findOne({ where: { id: list.id } }))?.reminderAt)
+      .toBe(reminderAt);
+    expect(listsService.publishListSnapshot).not.toHaveBeenCalled();
+  });
+
+  it('ignores reminders that are not due yet or soft deleted', async () => {
+    await saveList({
+      id: 'future-list',
+      reminderAt: new Date('2026-06-17T10:00:00.000Z'),
+      items: [{ title: 'Spaeter', checked: false, position: 0 }],
+    });
+    await saveList({
+      id: 'deleted-list',
+      deletedAt: new Date('2026-06-17T07:00:00.000Z'),
+      reminderAt: new Date('2026-06-17T08:00:00.000Z'),
+      items: [{ title: 'Archiviert', checked: false, position: 0 }],
+    });
+
+    await service.processDueReminders(new Date('2026-06-17T09:00:00.000Z'));
+
+    expect(mailService.sendListReminderEmail).not.toHaveBeenCalled();
+  });
+
+  async function saveList(
+    overrides: Partial<UserListEntity> & {
+      items?: Array<{ title: string; checked: boolean; position: number }>;
+    },
+  ): Promise<UserListEntity> {
+    const list = {
+      id: overrides.id ?? 'list-1',
+      ownerId: 'owner-1',
+      owner: {
+        id: 'owner-1',
+        email: 'owner@example.com',
+      } as UserEntity,
+      name: 'Testliste',
+      description: null,
+      kind: 'todo',
+      reminderAt: overrides.reminderAt ?? null,
+      deletedAt: overrides.deletedAt ?? null,
+      items: (overrides.items ?? []).map((item, index) => ({
+        id: `item-${index}`,
+        listId: overrides.id ?? 'list-1',
+        title: item.title,
+        checked: item.checked,
+        required: true,
+        position: item.position,
+        createdAt: new Date(),
+        updatedAt: new Date(),
+      })),
+      createdAt: new Date(),
+      updatedAt: new Date(),
+    } as UserListEntity;
+
+    return (await listsRepository.save(list)) as UserListEntity;
+  }
+});

listify-api/src/lists/list-reminder.service.ts

@@ -0,0 +1,127 @@
+import {
+  Injectable,
+  Logger,
+  OnModuleDestroy,
+  OnModuleInit,
+} from '@nestjs/common';
+import { ConfigService } from '@nestjs/config';
+import { InjectRepository } from '@nestjs/typeorm';
+import { IsNull, LessThanOrEqual, Repository } from 'typeorm';
+import { MailService } from '../mail/mail.service';
+import { UserListEntity } from './user-list.entity';
+import { ListsService } from './lists.service';
+
+@Injectable()
+export class ListReminderService implements OnModuleInit, OnModuleDestroy {
+  private readonly logger = new Logger(ListReminderService.name);
+  private timer?: NodeJS.Timeout;
+  private processing = false;
+
+  constructor(
+    @InjectRepository(UserListEntity)
+    private readonly listsRepository: Repository<UserListEntity>,
+    private readonly configService: ConfigService,
+    private readonly mailService: MailService,
+    private readonly listsService: ListsService,
+  ) {}
+
+  onModuleInit(): void {
+    if (process.env.NODE_ENV === 'test') {
+      return;
+    }
+
+    const intervalMs = Number(
+      this.configService.get<string>('LIST_REMINDER_POLL_INTERVAL_MS', '60000'),
+    );
+
+    this.timer = setInterval(
+      () => void this.processDueReminders(),
+      Number.isFinite(intervalMs) && intervalMs > 0 ? intervalMs : 60000,
+    );
+    void this.processDueReminders();
+  }
+
+  onModuleDestroy(): void {
+    if (this.timer) {
+      clearInterval(this.timer);
+      this.timer = undefined;
+    }
+  }
+
+  async processDueReminders(now = new Date()): Promise<void> {
+    if (this.processing) {
+      return;
+    }
+
+    this.processing = true;
+
+    try {
+      const lists = await this.listsRepository.find({
+        where: {
+          deletedAt: IsNull(),
+          reminderAt: LessThanOrEqual(now),
+        },
+        relations: { owner: true, items: true },
+        order: { reminderAt: 'ASC', items: { position: 'ASC' } },
+      });
+
+      for (const list of lists) {
+        await this.processListReminder(list);
+      }
+    } finally {
+      this.processing = false;
+    }
+  }
+
+  private async processListReminder(list: UserListEntity): Promise<void> {
+    const openItems = (list.items ?? [])
+      .filter((item) => !item.checked)
+      .sort((left, right) => left.position - right.position);
+
+    if (openItems.length === 0) {
+      await this.clearReminder(list);
+      return;
+    }
+
+    const ownerEmail = list.owner?.email;
+
+    if (!ownerEmail) {
+      this.logger.warn(`List reminder skipped because owner email is missing: ${list.id}`);
+      return;
+    }
+
+    try {
+      await this.mailService.sendListReminderEmail(ownerEmail, {
+        listId: list.id,
+        listName: list.name,
+        listUrl: this.listUrl(list.id),
+        openItems: openItems.map((item) => ({
+          title: item.title,
+          notes: item.notes ?? undefined,
+          quantity: item.quantity ?? undefined,
+        })),
+      });
+      await this.clearReminder(list);
+    } catch (error) {
+      this.logger.error(
+        `List reminder could not be sent for list ${list.id}.`,
+        error instanceof Error ? error.stack : undefined,
+      );
+    }
+  }
+
+  private async clearReminder(list: UserListEntity): Promise<void> {
+    list.reminderAt = null;
+    await this.listsRepository.save(list);
+    await this.listsService.publishListSnapshot(list.id);
+  }
+
+  private listUrl(listId: string): string {
+    const clientUrl = this.configService.get<string>(
+      'CLIENT_URL',
+      'http://localhost:4200',
+    );
+
+    return `${clientUrl.replace(/\/$/, '')}/lists/${listId}`;
+  }
+}

listify-api/src/lists/lists.module.ts

@@ -2,11 +2,13 @@ import { Module } from '@nestjs/common';
 import { TypeOrmModule } from '@nestjs/typeorm';
 import { AuditModule } from '../audit/audit.module';
 import { AuthModule } from '../auth/auth.module';
+import { MailModule } from '../mail/mail.module';
 import { UserEntity } from '../auth/user.entity';
 import { ListTemplateEntity } from '../list-templates/list-template.entity';
 import { ListTemplateItemEntity } from '../list-templates/list-template-item.entity';
 import { ListsController } from './lists.controller';
 import { ListRealtimeService } from './list-realtime.service';
+import { ListReminderService } from './list-reminder.service';
 import { ListsService } from './lists.service';
 import { UserListEntity } from './user-list.entity';
 import { UserListItemEntity } from './user-list-item.entity';
@@ -16,6 +18,7 @@ import { UserListShareEntity } from './user-list-share.entity';
   imports: [
     AuditModule,
     AuthModule,
+    MailModule,
     TypeOrmModule.forFeature([
       UserEntity,
       UserListEntity,
@@ -26,7 +29,7 @@ import { UserListShareEntity } from './user-list-share.entity';
     ]),
   ],
   controllers: [ListsController],
-  providers: [ListRealtimeService, ListsService],
+  providers: [ListRealtimeService, ListReminderService, ListsService],
   exports: [ListRealtimeService, ListsService],
 })
 export class ListsModule {}

listify-api/src/lists/lists.service.spec.ts

@@ -57,12 +57,42 @@ describe('ListsService', () => {
 
     expect(list.name).toBe('Sommerurlaub 2026');
     expect(list.kind).toBe('packing');
+    expect(list.reminderAt).toBeUndefined();
     expect(list.items).toHaveLength(0);
     expect(list.sourceTemplateId).toBeUndefined();
     await expect(service.listLists('user-1')).resolves.toHaveLength(1);
     await expect(service.listLists('user-2')).resolves.toHaveLength(0);
   });
 
+  it('creates, updates and clears list reminders', async () => {
+    const reminderAt = '2026-06-18T10:30:00.000Z';
+    const list = await service.createList('user-1', {
+      name: 'Reminder Liste',
+      reminderAt,
+    });
+
+    expect(list.reminderAt).toBe(reminderAt);
+
+    const updatedList = await service.updateList('user-1', list.id, {
+      reminderAt: '2026-06-19T08:15:00.000Z',
+    });
+    const clearedList = await service.updateList('user-1', list.id, {
+      reminderAt: null,
+    });
+
+    expect(updatedList.reminderAt).toBe('2026-06-19T08:15:00.000Z');
+    expect(clearedList.reminderAt).toBeUndefined();
+  });
+
+  it('rejects invalid list reminder timestamps', async () => {
+    await expect(
+      service.createList('user-1', {
+        name: 'Reminder Liste',
+        reminderAt: 'not-a-date',
+      }),
+    ).rejects.toThrow('Reminder time must be an ISO date string.');
+  });
+
   it('updates and deletes concrete lists', async () => {
     const list = await service.createList('user-1', {
       name: 'Todo',

listify-api/src/lists/lists.service.ts

@@ -91,6 +91,7 @@ export class ListsService {
       name: this.requireName(createDto.name),
       description: this.normalizeOptionalText(createDto.description),
       kind: this.normalizeKind(createDto.kind),
+      reminderAt: this.normalizeReminderAt(createDto.reminderAt) ?? null,
       deletedAt: null,
       items: [],
     });
@@ -245,6 +246,10 @@ export class ListsService {
       list.kind = this.normalizeKind(updateDto.kind);
     }
 
+    if (updateDto.reminderAt !== undefined) {
+      list.reminderAt = this.normalizeReminderAt(updateDto.reminderAt);
+    }
+
     const savedList = await this.listsRepository.save(list);
 
     await this.auditLogService?.record({
@@ -719,6 +724,34 @@ export class ListsService {
     return value;
   }
 
+  private normalizeReminderAt(value?: string | null): Date | null | undefined {
+    if (value === undefined) {
+      return undefined;
+    }
+
+    if (value === null) {
+      return null;
+    }
+
+    if (typeof value !== 'string') {
+      throw new BadRequestException('Reminder time must be an ISO date string.');
+    }
+
+    const normalizedValue = value.trim();
+
+    if (!normalizedValue) {
+      return null;
+    }
+
+    const reminderAt = new Date(normalizedValue);
+
+    if (Number.isNaN(reminderAt.getTime())) {
+      throw new BadRequestException('Reminder time must be an ISO date string.');
+    }
+
+    return reminderAt;
+  }
+
   private requireShareUserId(userId?: string): string {
     const normalizedUserId = userId?.trim();
 
@@ -768,7 +801,7 @@ export class ListsService {
     }
   }
 
-  private async publishListSnapshot(listId: string): Promise<void> {
+  async publishListSnapshot(listId: string): Promise<void> {
     if (!this.listRealtimeService) {
       return;
     }
@@ -804,6 +837,7 @@ export class ListsService {
       name: list.name,
       description: list.description ?? undefined,
       kind: list.kind,
+      reminderAt: list.reminderAt ? this.toIsoString(list.reminderAt) : undefined,
       items: (list.items ?? [])
         .sort((left, right) => left.position - right.position)
         .map((item) => this.toUserListItem(item)),

listify-api/src/lists/user-list.entity.ts

@@ -35,6 +35,10 @@ export class UserListEntity {
   @Column({ type: 'varchar', length: 32, default: 'custom' })
   kind!: ListTemplateKind;
 
+  @Index('IDX_user_lists_reminder_at')
+  @Column({ type: 'datetime', precision: 3, nullable: true })
+  reminderAt?: Date | null;
+
   @CreateDateColumn({
     type: 'datetime',
     precision: 3,

listify-api/src/mail/mail.service.ts

@@ -4,13 +4,14 @@ import { MailerService } from '@nestjs-modules/mailer';
 import { existsSync, readFileSync } from 'fs';
 import { compile, TemplateDelegate } from 'handlebars';
 import { join } from 'path';
-import { SentEmail } from './mail.types';
+import { ListReminderEmailPayload, SentEmail } from './mail.types';
 
 @Injectable()
 export class MailService {
   private readonly logger = new Logger(MailService.name);
   private readonly sentEmails: SentEmail[] = [];
   private verificationTemplate?: TemplateDelegate;
+  private listReminderTemplate?: TemplateDelegate;
 
   constructor(
     private readonly configService: ConfigService,
@@ -70,6 +71,63 @@ export class MailService {
     }
   }
 
+  async sendListReminderEmail(
+    to: string,
+    payload: ListReminderEmailPayload,
+  ): Promise<void> {
+    const subject = `Erinnerung: ${payload.listName}`;
+    const openItemLines = payload.openItems.map((item) => `- ${item.title}`);
+    const email: SentEmail = {
+      to,
+      subject,
+      text: [
+        `Erinnerung fuer deine Liste "${payload.listName}".`,
+        '',
+        'Offene Punkte:',
+        ...openItemLines,
+        '',
+        `Liste oeffnen: ${payload.listUrl}`,
+      ].join('\n'),
+      listId: payload.listId,
+      listUrl: payload.listUrl,
+      openItemTitles: payload.openItems.map((item) => item.title),
+    };
+
+    this.sentEmails.push(email);
+
+    if (!this.mailEnabled()) {
+      this.logger.log(`List reminder email queued for ${to}. Mail sending is disabled.`);
+      return;
+    }
+
+    try {
+      await this.mailerService.sendMail({
+        to,
+        subject: email.subject,
+        text: email.text,
+        html: this.renderListReminderTemplate({
+          appName: this.configService.get<string>('MAIL_FROM_NAME', 'Listify'),
+          clientUrl: this.configService.get<string>(
+            'CLIENT_URL',
+            'http://localhost:4200',
+          ),
+          listName: payload.listName,
+          listUrl: payload.listUrl,
+          openItems: payload.openItems,
+          openItemCount: payload.openItems.length,
+          currentYear: new Date().getFullYear(),
+        }),
+      });
+      this.logger.log(`List reminder email sent to ${to}.`);
+    } catch (error) {
+      this.logger.error(
+        `List reminder email could not be sent to ${to}.`,
+        error instanceof Error ? error.stack : undefined,
+      );
+      throw error;
+    }
+  }
+
   getSentEmails(): SentEmail[] {
     return [...this.sentEmails];
   }
@@ -89,6 +147,23 @@ export class MailService {
     return this.verificationTemplate(context);
   }
 
+  private renderListReminderTemplate(context: {
+    appName: string;
+    clientUrl: string;
+    listName: string;
+    listUrl: string;
+    openItems: ListReminderEmailPayload['openItems'];
+    openItemCount: number;
+    currentYear: number;
+  }): string {
+    this.listReminderTemplate ??= compile(
+      readFileSync(this.resolveTemplatePath('list-reminder.hbs'), 'utf8'),
+      { strict: true },
+    );
+
+    return this.listReminderTemplate(context);
+  }
+
   private resolveTemplatePath(fileName: string): string {
     const candidates = [
       join(process.cwd(), 'dist', 'mail', 'templates', fileName),

listify-api/src/mail/mail.types.ts

@@ -2,5 +2,21 @@ export interface SentEmail {
   to: string;
   subject: string;
   text: string;
-  verificationUrl: string;
+  verificationUrl?: string;
+  listId?: string;
+  listUrl?: string;
+  openItemTitles?: string[];
+}
+
+export interface ListReminderEmailItem {
+  title: string;
+  notes?: string;
+  quantity?: number;
+}
+
+export interface ListReminderEmailPayload {
+  listId: string;
+  listName: string;
+  listUrl: string;
+  openItems: ListReminderEmailItem[];
 }

listify-api/src/mail/templates/list-reminder.hbs

@@ -0,0 +1,63 @@
+<!doctype html>
+<html lang="de">
+  <head>
+    <meta charset="utf-8" />
+    <meta name="viewport" content="width=device-width, initial-scale=1" />
+    <title>Listify Erinnerung</title>
+  </head>
+  <body style="margin:0;background:#f4f7f5;font-family:Arial,Helvetica,sans-serif;color:#17211b;">
+    <table role="presentation" width="100%" cellspacing="0" cellpadding="0" style="background:#f4f7f5;padding:24px 12px;">
+      <tr>
+        <td align="center">
+          <table role="presentation" width="100%" cellspacing="0" cellpadding="0" style="max-width:560px;background:#ffffff;border:1px solid #dce5df;border-radius:8px;overflow:hidden;">
+            <tr>
+              <td style="padding:28px 28px 18px;background:#0f5f3d;color:#ffffff;">
+                <div style="font-size:14px;letter-spacing:.08em;text-transform:uppercase;opacity:.85;">{{appName}}</div>
+                <h1 style="margin:10px 0 0;font-size:26px;line-height:1.2;font-weight:700;">Erinnerung fuer {{listName}}</h1>
+              </td>
+            </tr>
+
+            <tr>
+              <td style="padding:28px;">
+                <p style="margin:0 0 18px;font-size:16px;line-height:1.55;">
+                  In deiner Liste sind noch {{openItemCount}} Punkte offen:
+                </p>
+
+                <ul style="margin:0 0 24px;padding-left:22px;font-size:16px;line-height:1.55;">
+                  {{#each openItems}}
+                    <li style="margin:0 0 8px;">
+                      <strong>{{title}}</strong>
+                      {{#if quantity}}<span style="color:#52645a;"> - Menge: {{quantity}}</span>{{/if}}
+                      {{#if notes}}<div style="color:#52645a;font-size:14px;">{{notes}}</div>{{/if}}
+                    </li>
+                  {{/each}}
+                </ul>
+
+                <table role="presentation" cellspacing="0" cellpadding="0" style="margin:24px 0;">
+                  <tr>
+                    <td>
+                      <a href="{{listUrl}}" style="display:inline-block;background:#0f5f3d;color:#ffffff;text-decoration:none;border-radius:6px;padding:14px 20px;font-size:16px;font-weight:700;">
+                        Liste oeffnen
+                      </a>
+                    </td>
+                  </tr>
+                </table>
+
+                <p style="margin:0;padding:12px;background:#eef4f0;border:1px solid #dce5df;border-radius:6px;font-size:13px;line-height:1.45;word-break:break-all;">
+                  <a href="{{listUrl}}" style="color:#0f5f3d;">{{listUrl}}</a>
+                </p>
+              </td>
+            </tr>
+
+            <tr>
+              <td style="padding:18px 28px;background:#f8faf8;border-top:1px solid #e7eee9;color:#6a7b71;font-size:12px;line-height:1.5;">
+                <div>{{appName}} - Listen, Templates und gemeinsame Planung.</div>
+                <div style="margin-top:4px;">&copy; {{currentYear}} {{appName}}</div>
+              </td>
+            </tr>
+          </table>
+        </td>
+      </tr>
+    </table>
+  </body>
+</html>

listify-api/src/testing/in-memory-repository.ts

@@ -91,13 +91,34 @@ export class InMemoryRepository<T extends object> {
         return recordValue === null || recordValue === undefined;
       }
 
+      if (value instanceof FindOperator && value.type === 'lessThanOrEqual') {
+        const operatorValue = value.value as unknown;
+
+        if (recordValue instanceof Date && operatorValue instanceof Date) {
+          return recordValue.getTime() <= operatorValue.getTime();
+        }
+
+        if (
+          (typeof recordValue === 'number' || typeof recordValue === 'string') &&
+          (typeof operatorValue === 'number' || typeof operatorValue === 'string')
+        ) {
+          return recordValue <= operatorValue;
+        }
+
+        return false;
+      }
+
       return recordValue === value;
     });
   }
 
   private applyOrder(records: T[], order: unknown): T[] {
     const sortedRecords = [...records];
-    const typedOrder = order as { name?: 'ASC' | 'DESC'; items?: { position?: 'ASC' | 'DESC' } };
+    const typedOrder = order as {
+      name?: 'ASC' | 'DESC';
+      reminderAt?: 'ASC' | 'DESC';
+      items?: { position?: 'ASC' | 'DESC' };
+    };
 
     if (typedOrder?.name) {
       sortedRecords.sort((left, right) => {
@@ -109,6 +130,18 @@ export class InMemoryRepository<T extends object> {
       });
     }
 
+    if (typedOrder?.reminderAt) {
+      sortedRecords.sort((left, right) => {
+        const leftDate = (left as Record<string, unknown>)['reminderAt'];
+        const rightDate = (right as Record<string, unknown>)['reminderAt'];
+        const leftTime = leftDate instanceof Date ? leftDate.getTime() : 0;
+        const rightTime = rightDate instanceof Date ? rightDate.getTime() : 0;
+        return typedOrder.reminderAt === 'DESC'
+          ? rightTime - leftTime
+          : leftTime - rightTime;
+      });
+    }
+
     if (typedOrder?.items?.position) {
       for (const record of sortedRecords) {
         const items = (record as { items?: Array<{ position: number }> }).items;

listify-client/src/app/lists/list-detail/list-detail.component.html

@@ -99,6 +99,23 @@
               <textarea matInput formControlName="description" rows="4"></textarea>
             </mat-form-field>
 
+            <mat-form-field appearance="outline">
+              <mat-label>E-Mail-Erinnerung</mat-label>
+              <input matInput type="datetime-local" formControlName="reminderAt" />
+              <mat-icon matPrefix aria-hidden="true">notifications</mat-icon>
+              @if (listForm.controls.reminderAt.value) {
+                <button
+                  mat-icon-button
+                  matSuffix
+                  type="button"
+                  aria-label="Erinnerung entfernen"
+                  (click)="clearReminder()"
+                >
+                  <mat-icon aria-hidden="true">close</mat-icon>
+                </button>
+              }
+            </mat-form-field>
+
             <div class="list-form-actions" [class.create-actions]="isCreateMode()">
               <button mat-flat-button type="submit" [disabled]="saving() || creatingWithAi()">
                 @if (saving()) {
@@ -129,6 +146,14 @@
         } @else {
           <div class="list-summary">
             <p>{{ list()?.description || 'Keine Beschreibung hinterlegt.' }}</p>
+            @if (list()?.reminderAt) {
+              <div class="inline-empty">
+                <mat-icon aria-hidden="true">notifications</mat-icon>
+                <span>
+                  Erinnerung am {{ list()!.reminderAt | date: 'dd.MM.yyyy, HH:mm' }}
+                </span>
+              </div>
+            }
           </div>
         }
       </mat-card-content>

listify-client/src/app/lists/list-detail/list-detail.component.ts

@@ -105,6 +105,7 @@ export class ListDetailComponent implements OnInit {
   protected readonly listForm = this.formBuilder.group({
     name: ['', [Validators.required]],
     description: [''],
+    reminderAt: [''],
   });
 
   protected readonly itemForm = this.formBuilder.group({
@@ -118,7 +119,7 @@ export class ListDetailComponent implements OnInit {
     if (this.isCreateMode()) {
       this.loading.set(false);
       this.editing.set(true);
-      this.listForm.reset({ name: '', description: '' });
+      this.listForm.reset({ name: '', description: '', reminderAt: '' });
       return;
     }
 
@@ -420,6 +421,7 @@ export class ListDetailComponent implements OnInit {
       this.listForm.reset({
         name: list.name,
         description: list.description ?? '',
+        reminderAt: this.toDatetimeLocalValue(list.reminderAt),
       });
     }
 
@@ -544,6 +546,7 @@ export class ListDetailComponent implements OnInit {
       this.listForm.reset({
         name: list.name,
         description: list.description ?? '',
+        reminderAt: this.toDatetimeLocalValue(list.reminderAt),
       });
     }
   }
@@ -562,9 +565,40 @@ export class ListDetailComponent implements OnInit {
     return {
       name: formValue.name.trim(),
       description: formValue.description.trim() || undefined,
+      reminderAt: this.datetimeLocalToIso(formValue.reminderAt),
     };
   }
 
+  protected clearReminder(): void {
+    this.listForm.controls.reminderAt.setValue('');
+  }
+
+  private datetimeLocalToIso(value: string): string | null {
+    const normalizedValue = value.trim();
+
+    if (!normalizedValue) {
+      return null;
+    }
+
+    const date = new Date(normalizedValue);
+    return Number.isNaN(date.getTime()) ? null : date.toISOString();
+  }
+
+  private toDatetimeLocalValue(value?: string | null): string {
+    if (!value) {
+      return '';
+    }
+
+    const date = new Date(value);
+
+    if (Number.isNaN(date.getTime())) {
+      return '';
+    }
+
+    const timezoneOffsetMs = date.getTimezoneOffset() * 60 * 1000;
+    return new Date(date.getTime() - timezoneOffsetMs).toISOString().slice(0, 16);
+  }
+
   private uncheckedFirst(items: UserListItem[]): UserListItem[] {
     return items
       .map((item, index) => ({ item, index }))

listify-client/src/app/lists/lists.component.html

@@ -144,6 +144,12 @@
                 <mat-icon aria-hidden="true">schedule</mat-icon>
                 {{ list.updatedAt | date: 'dd.MM.yyyy' }}
               </span>
+              @if (list.reminderAt) {
+                <span>
+                  <mat-icon aria-hidden="true">notifications</mat-icon>
+                  {{ list.reminderAt | date: 'dd.MM.yyyy, HH:mm' }}
+                </span>
+              }
               @if (list.collaborators.length > 0) {
                 <span>
                   <mat-icon aria-hidden="true">group</mat-icon>

listify-client/src/app/lists/lists.models.ts

@@ -35,6 +35,7 @@ export interface UserList {
   name: string;
   description?: string;
   kind: ListTemplateKind;
+  reminderAt?: string | null;
   items: UserListItem[];
   collaborators: UserListCollaborator[];
   createdAt: string;
@@ -45,12 +46,14 @@ export interface CreateListRequest {
   name: string;
   description?: string;
   kind?: ListTemplateKind;
+  reminderAt?: string | null;
 }
 
 export interface UpdateListRequest {
   name?: string;
   description?: string;
   kind?: ListTemplateKind;
+  reminderAt?: string | null;
 }
 
 export interface AddListItemRequest {

listify-client/src/app/templates/templates.models.ts

@@ -42,6 +42,7 @@ export interface UserList {
   name: string;
   description?: string;
   kind: ListTemplateKind;
+  reminderAt?: string | null;
   items: UserListItem[];
   createdAt: string;
   updatedAt: string;