apps/web/src/editor/document-extensions.ts

@@ -7,6 +7,7 @@ import { BulletList, ListItem, OrderedList, TaskList } from './nodes/lists';
 import { PluginBlock } from './nodes/plugin-block';
 import { Table, TableCell, TableHeader, TableRow } from './nodes/table';
 import { TaskItem } from './nodes/task-item';
+import { DateMarker } from './nodes/date-marker';
 import { Mention } from './nodes/mention';
 import { Transclusion } from './nodes/transclusion';
 import { Wikilink } from './nodes/wikilink';
@@ -46,6 +47,7 @@ export const documentExtensions: AnyExtension[] = [
   PluginBlock,
   Wikilink,
   Mention,
+  DateMarker,
   Transclusion,
   Table,
   TableRow,

apps/web/src/editor/nodes/date-marker.tsx

@@ -0,0 +1,91 @@
+import { InputRule, Node } from '@tiptap/core';
+import { NodeViewWrapper, ReactNodeViewRenderer } from '@tiptap/react';
+import type { NodeViewProps } from '@tiptap/react';
+import { useTranslation } from 'react-i18next';
+
+import { attributesFromSpec, nodeSpec } from '../spec-utils';
+
+/** `>>`/`<<` + ISO or `dd.mm.yyyy`, completed by a space (the trigger). */
+const INPUT_PATTERN =
+  /(?:^|\s)([<>])\1\s?(?:(\d{4})-(\d{2})-(\d{2})|(\d{1,2})\.(\d{1,2})\.(\d{4}))\s$/;
+
+function isoDateOf(match: RegExpMatchArray): string | null {
+  const [year, month, day] = match[2]
+    ? [Number(match[2]), Number(match[3]), Number(match[4])]
+    : [Number(match[7]), Number(match[6]), Number(match[5])];
+  const date = new Date(Date.UTC(year, month - 1, day));
+  const valid =
+    date.getUTCFullYear() === year && date.getUTCMonth() === month - 1 && date.getUTCDate() === day;
+  if (!valid) return null;
+  const pad = (value: number): string => String(value).padStart(2, '0');
+  return `${year}-${pad(month)}-${pad(day)}`;
+}
+
+/**
+ * Renders a date marker (issue #152): `»` = due date (`>>`), `«` = start
+ * date (`<<`), formatted per the viewer's language. A due date in the past
+ * gets an "overdue" tint. The stored attr is always canonical ISO.
+ */
+function DateMarkerView({ node }: NodeViewProps): React.JSX.Element {
+  const { t, i18n } = useTranslation('editor');
+  const kind = node.attrs.kind as 'due' | 'start';
+  const iso = node.attrs.date as string;
+
+  const formatted = new Intl.DateTimeFormat(i18n.language, { dateStyle: 'medium' }).format(
+    new Date(`${iso}T00:00:00`),
+  );
+  const overdue = kind === 'due' && iso < new Date().toISOString().slice(0, 10);
+  const classes = ['dt-date', `dt-date--${kind}`];
+  if (overdue) classes.push('dt-date--overdue');
+
+  return (
+    <NodeViewWrapper as="span" className="dt-date-nodeview">
+      <span
+        className={classes.join(' ')}
+        title={t(kind === 'due' ? 'dateMarker.due' : 'dateMarker.start')}
+        contentEditable={false}
+      >
+        {kind === 'due' ? '»' : '«'} {formatted}
+      </span>
+    </NodeViewWrapper>
+  );
+}
+
+const dateMarkerSpec = nodeSpec('date_marker');
+export const DateMarker = Node.create({
+  name: 'date_marker',
+  group: dateMarkerSpec.group,
+  inline: dateMarkerSpec.inline,
+  atom: dateMarkerSpec.atom,
+  addAttributes() {
+    return attributesFromSpec(dateMarkerSpec);
+  },
+  parseHTML: () => dateMarkerSpec.parseDOM,
+  renderHTML: ({ node }) => dateMarkerSpec.toDOM!(node),
+  addInputRules() {
+    return [
+      new InputRule({
+        find: INPUT_PATTERN,
+        handler: ({ range, match, chain }) => {
+          const iso = isoDateOf(match);
+          if (!iso) return;
+          // Keep a leading boundary character (space/line start) intact.
+          const full = match[0];
+          const markerStart = range.from + (full.length - full.trimStart().length);
+          chain()
+            .insertContentAt({ from: markerStart, to: range.to }, [
+              {
+                type: 'date_marker',
+                attrs: { kind: match[1] === '>' ? 'due' : 'start', date: iso },
+              },
+              { type: 'text', text: ' ' },
+            ])
+            .run();
+        },
+      }),
+    ];
+  },
+  addNodeView() {
+    return ReactNodeViewRenderer(DateMarkerView);
+  },
+});

apps/web/src/styles/base.css

@@ -3824,3 +3824,22 @@ ul[data-type='task_list'] li p:last-of-type {
   color: var(--color-text-muted);
   text-decoration: line-through;
 }
+
+/* Date marker chip (issue #152): » = due date, « = start date. */
+.dt-date {
+  display: inline-block;
+  padding: 0 0.35em;
+  border-radius: 6px;
+  background: var(--color-bg-subtle);
+  color: var(--color-text-muted);
+  white-space: nowrap;
+  font-variant-numeric: tabular-nums;
+}
+
+.dt-date--due {
+  color: var(--color-accent);
+}
+
+.dt-date--overdue {
+  color: #b91c1c;
+}

packages/shared/i18n/de/editor.json

@@ -185,5 +185,9 @@
   "mention": {
     "unresolved": "Unbekannter Nutzer",
     "suggestLabel": "Nutzer-Vorschläge"
+  },
+  "dateMarker": {
+    "due": "Zieldatum",
+    "start": "Startdatum"
   }
 }

packages/shared/i18n/en/editor.json

@@ -185,5 +185,9 @@
   "mention": {
     "unresolved": "Unknown user",
     "suggestLabel": "User suggestions"
+  },
+  "dateMarker": {
+    "due": "Due date",
+    "start": "Start date"
   }
 }

packages/shared/src/editor-schema/date-marker.test.ts

@@ -0,0 +1,73 @@
+import { Node } from 'prosemirror-model';
+import { describe, expect, it } from 'vitest';
+
+import { docToHtml } from './html';
+import { docToMarkdown, markdownToDoc } from './markdown';
+import { docToPlainText } from './plain-text';
+
+function markers(doc: Node): { kind: string; date: string }[] {
+  const found: { kind: string; date: string }[] = [];
+  doc.descendants((node) => {
+    if (node.type.name === 'date_marker') {
+      found.push({ kind: node.attrs.kind as string, date: node.attrs.date as string });
+    }
+  });
+  return found;
+}
+
+describe('date markers >>/<< (issue #152)', () => {
+  it('parses ISO due and start dates and round-trips canonically', () => {
+    const doc = markdownToDoc('Projekt <<2026-07-01 bis >>2026-12-31 fertig.');
+    expect(markers(doc)).toEqual([
+      { kind: 'start', date: '2026-07-01' },
+      { kind: 'due', date: '2026-12-31' },
+    ]);
+    const markdown = docToMarkdown(doc);
+    expect(markdown).toContain('<<2026-07-01');
+    expect(markdown).toContain('>>2026-12-31');
+  });
+
+  it('accepts dd.mm.yyyy as input lenience but serializes ISO', () => {
+    const doc = markdownToDoc('Zieltermin >>31.12.2026 bitte.');
+    expect(markers(doc)).toEqual([{ kind: 'due', date: '2026-12-31' }]);
+    expect(docToMarkdown(doc)).toContain('>>2026-12-31');
+  });
+
+  it('keeps a line-leading >>date out of blockquote parsing', () => {
+    const doc = markdownToDoc('>>2026-12-31 ist die Deadline.');
+    expect(markers(doc)).toEqual([{ kind: 'due', date: '2026-12-31' }]);
+    let quotes = 0;
+    doc.descendants((node) => {
+      if (node.type.name === 'blockquote') quotes += 1;
+    });
+    expect(quotes).toBe(0);
+    // A real blockquote still works.
+    const quote = markdownToDoc('> ein Zitat');
+    let realQuotes = 0;
+    quote.descendants((node) => {
+      if (node.type.name === 'blockquote') realQuotes += 1;
+    });
+    expect(realQuotes).toBe(1);
+  });
+
+  it('leaves invalid calendar dates as plain text', () => {
+    const doc = markdownToDoc('Kaputt: >>31.02.2026 bleibt Text.');
+    expect(markers(doc)).toEqual([]);
+    expect(docToMarkdown(doc)).toContain('31.02.2026');
+  });
+
+  it('renders HTML with kind, ISO date, and shows up in plain text', () => {
+    const doc = markdownToDoc('Bis >>2026-12-31.');
+    const html = docToHtml(doc);
+    expect(html).toContain('data-date-marker="due"');
+    expect(html).toContain('data-date="2026-12-31"');
+    expect(docToPlainText(doc)).toContain('2026-12-31');
+  });
+
+  it('works inside task list lines', () => {
+    const doc = markdownToDoc('- [ ] Bühne buchen >>2026-08-01 @nadia');
+    expect(markers(doc)).toEqual([{ kind: 'due', date: '2026-08-01' }]);
+    const markdown = docToMarkdown(doc);
+    expect(markdown).toContain('- [ ] Bühne buchen >>2026-08-01 @nadia');
+  });
+});

packages/shared/src/editor-schema/html.ts

@@ -69,6 +69,14 @@ function renderInline(node: Node): string {
       const text = escapeHtml(display ?? (child.attrs.targetSlug as string));
       const displayAttr = display ? ` data-display="${escapeHtml(display)}"` : '';
       out += `<a class="wikilink" href="${slug}" data-wikilink="${slug}"${displayAttr}>${text}</a>`;
+    } else if (child.type.name === 'date_marker') {
+      // A date marker (issue #152): static HTML shows the unambiguous ISO
+      // date; locale-aware formatting happens where the viewer is known.
+      const kind = escapeHtml(child.attrs.kind as string);
+      const date = escapeHtml(child.attrs.date as string);
+      out +=
+        `<span class="dt-date dt-date--${kind}" data-date-marker="${kind}"` +
+        ` data-date="${date}">${kind === 'due' ? '»' : '«'} ${date}</span>`;
     } else if (child.type.name === 'mention') {
       // A user mention (issue #150): static HTML shows the @username; the
       // stable user id rides along for consumers that can resolve it.

packages/shared/src/editor-schema/markdown.ts

@@ -192,6 +192,82 @@ function wikilinkRule(state: StateInline, silent: boolean): boolean {
   return true;
 }
 
+/** `>>`/`<<` + ISO or `dd.mm.yyyy` date (issue #152). */
+const DATE_MARKER = /^([<>])\1\s?(?:(\d{4})-(\d{2})-(\d{2})|(\d{1,2})\.(\d{1,2})\.(\d{4}))/;
+
+/** Canonical `YYYY-MM-DD` from the regex groups, or null for a non-date. */
+function isoDateOf(match: RegExpExecArray): string | null {
+  const [year, month, day] = match[2]
+    ? [Number(match[2]), Number(match[3]), Number(match[4])]
+    : [Number(match[7]), Number(match[6]), Number(match[5])];
+  const date = new Date(Date.UTC(year, month - 1, day));
+  const valid =
+    date.getUTCFullYear() === year && date.getUTCMonth() === month - 1 && date.getUTCDate() === day;
+  if (!valid) return null;
+  const pad = (value: number): string => String(value).padStart(2, '0');
+  return `${year}-${pad(month)}-${pad(day)}`;
+}
+
+/** markdown-it inline rule for date markers (issue #152): `>>` = due date,
+ * `<<` = start date; ISO is canonical, `dd.mm.yyyy` is accepted as input
+ * lenience. An invalid calendar date stays plain text. */
+function dateMarkerRule(state: StateInline, silent: boolean): boolean {
+  const match = DATE_MARKER.exec(state.src.slice(state.pos));
+  if (!match) return false;
+  const iso = isoDateOf(match);
+  if (!iso) return false;
+  if (!silent) {
+    const token = state.push('date_marker', '', 0);
+    token.attrs = [
+      ['kind', match[1] === '>' ? 'due' : 'start'],
+      ['date', iso],
+    ];
+  }
+  state.pos += match[0].length;
+  return true;
+}
+
+/** Block guard (issue #152): a line starting with `>>2026-…` is a paragraph
+ * with a due-date marker, not a nested blockquote — registered before
+ * `blockquote` so markdown-it never sees the `>` as a quote. */
+function dateLineRule(
+  state: StateBlock,
+  startLine: number,
+  endLine: number,
+  silent: boolean,
+): boolean {
+  const start = state.bMarks[startLine]! + state.tShift[startLine]!;
+  const max = state.eMarks[startLine]!;
+  const match = DATE_MARKER.exec(state.src.slice(start, max));
+  if (!match || !isoDateOf(match)) return false;
+  if (silent) return true;
+  // Consume the paragraph like markdown-it's own paragraph rule would.
+  const terminatorRules = state.md.block.ruler.getRules('paragraph');
+  let nextLine = startLine + 1;
+  for (; nextLine < endLine && !state.isEmpty(nextLine); nextLine += 1) {
+    if (state.sCount[nextLine]! - state.blkIndent > 3) continue;
+    if (state.sCount[nextLine]! < 0) continue;
+    let terminate = false;
+    for (const rule of terminatorRules) {
+      if (rule(state, nextLine, endLine, true)) {
+        terminate = true;
+        break;
+      }
+    }
+    if (terminate) break;
+  }
+  const content = state.getLines(startLine, nextLine, state.blkIndent, false).trim();
+  const open = state.push('paragraph_open', 'p', 1);
+  open.map = [startLine, nextLine];
+  const inline = state.push('inline', '', 0);
+  inline.content = content;
+  inline.map = [startLine, nextLine];
+  inline.children = [];
+  state.push('paragraph_close', 'p', -1);
+  state.line = nextLine;
+  return true;
+}
+
 /** Username shape after the `@` (mirrors the signup `usernameSchema`). */
 const MENTION_NAME = /^[a-z0-9](?:[a-z0-9-]*[a-z0-9])?/i;
 
@@ -308,6 +384,10 @@ function createTokenizer(): MarkdownIt {
   md.inline.ruler.before('link', 'wikilink', wikilinkRule);
   // `@username` mentions (issue #150).
   md.inline.ruler.before('link', 'mention', mentionRule);
+  // `>>`/`<<` date markers (issue #152) …
+  md.inline.ruler.before('link', 'date_marker', dateMarkerRule);
+  // … and the guard that keeps a line-leading `>>date` out of blockquote.
+  md.block.ruler.before('blockquote', 'date_line', dateLineRule);
   // Run before `paragraph` so a lone `![[slug]]` line embeds rather than reads
   // as plain text (issue #135).
   md.block.ruler.before('paragraph', 'transclusion', transclusionRule);
@@ -383,6 +463,13 @@ const markdownParser = new MarkdownParser(editorSchema, createTokenizer(), {
       userId: tok.attrGet('userId') ?? '',
     }),
   },
+  date_marker: {
+    node: 'date_marker',
+    getAttrs: (tok) => ({
+      kind: tok.attrGet('kind') ?? 'due',
+      date: tok.attrGet('date') ?? '',
+    }),
+  },
   transclusion: {
     node: 'transclusion',
     getAttrs: (tok) => ({
@@ -517,6 +604,10 @@ const markdownSerializer = new MarkdownSerializer(
     mention(state, node) {
       state.write(`@${node.attrs.username as string}`);
     },
+    date_marker(state, node) {
+      const prefix = node.attrs.kind === 'due' ? '>>' : '<<';
+      state.write(`${prefix}${node.attrs.date as string}`);
+    },
     transclusion(state, node) {
       const slug = node.attrs.targetSlug as string;
       const display = node.attrs.displayText as string | null;

packages/shared/src/editor-schema/plain-text.ts

@@ -11,6 +11,8 @@ export function docToPlainText(doc: Node): string {
     }
     // A mention reads as `@username` (issue #150), so search finds it.
     if (leaf.type.name === 'mention') return `@${leaf.attrs.username as string}`;
+    // A date marker contributes its ISO date (issue #152).
+    if (leaf.type.name === 'date_marker') return leaf.attrs.date as string;
     return '';
   });
   return text.replace(/\n{3,}/g, '\n\n').trim();

packages/shared/src/editor-schema/schema.ts

@@ -256,6 +256,38 @@ export const editorSchema = new Schema({
       },
     },
 
+    // `>>2026-12-31` / `<<2026-07-01` date marker (issue #152). An inline
+    // atom carrying a kind ('due' for `>>`, 'start' for `<<`) and the date as
+    // a canonical ISO `YYYY-MM-DD` string; locale-aware formatting happens in
+    // the editor, where the viewer's language is known.
+    date_marker: {
+      group: 'inline',
+      inline: true,
+      atom: true,
+      attrs: {
+        kind: { validate: 'string' },
+        date: { validate: 'string' },
+      },
+      parseDOM: [
+        {
+          tag: 'span[data-date-marker]',
+          getAttrs: (dom) => ({
+            kind: dom.getAttribute('data-date-marker'),
+            date: dom.getAttribute('data-date'),
+          }),
+        },
+      ],
+      toDOM: (node) => {
+        const kind = node.attrs.kind as string;
+        const date = node.attrs.date as string;
+        return [
+          'span',
+          { 'data-date-marker': kind, 'data-date': date, class: `dt-date dt-date--${kind}` },
+          `${kind === 'due' ? '»' : '«'} ${date}`,
+        ];
+      },
+    },
+
     // `@username` user mention (issue #150). An inline atom carrying the
     // mentioned user's stable id plus the username as serialization/display
     // fallback. Live display-name resolution happens in the editor where a