custom date/time formats

backend/utils.py

@@ -964,21 +964,45 @@ def get_template_content(notes_dir: str, template_name: str) -> Optional[str]:
         return None
 
 
+# Matches custom strftime placeholders like {{date:%Y%m%d}} or {{time:%H%M%S}}.
+# The three prefixes mirror the bare {{date}}, {{time}}, {{datetime}} placeholders;
+# disallowing '{' and '}' inside the format keeps parsing unambiguous and
+# guarantees we never swallow an adjacent placeholder.
+_STRFTIME_PLACEHOLDER_RE = re.compile(r'\{\{(date|time|datetime):([^{}]+)\}\}')
+
+
 def apply_template_placeholders(content: str, note_path: str) -> str:
     """
     Replace template placeholders with actual values.
 
-    Supported placeholders:
+    Built-in named placeholders (fixed default formats):
         {{date}}       - Current date (YYYY-MM-DD)
         {{time}}       - Current time (HH:MM:SS)
         {{datetime}}   - Current datetime (YYYY-MM-DD HH:MM:SS)
-        {{timestamp}}  - Unix timestamp
+        {{timestamp}}  - Unix timestamp (seconds)
         {{year}}       - Current year (YYYY)
         {{month}}      - Current month (MM)
         {{day}}        - Current day (DD)
         {{title}}      - Note name without extension
         {{folder}}     - Parent folder name
 
+    Custom date/time formats (strftime escape hatch):
+        {{date:FMT}}, {{time:FMT}}, {{datetime:FMT}}
+
+        Any of the three date/time placeholders above also accepts an
+        optional ":FMT" suffix where FMT is a Python strftime() format
+        string. Pick the prefix whose default format covers the same
+        components you want to format. Examples:
+
+            {{datetime:%Y%m%d%H%M%S}}  -> 20260506154200  (filename-safe stamp)
+            {{date:%d/%m/%Y}}          -> 06/05/2026      (European date)
+            {{date:%A}}                -> Wednesday       (full weekday name)
+            {{time:%H%M%S}}            -> 154200          (compact time)
+            {{date:%V}}                -> 19              (ISO week number)
+
+        Invalid format strings are left in the output unchanged so a typo
+        is visible rather than silently swallowed.
+
     Args:
         content: Template content with placeholders
         note_path: Path of the note being created
@@ -989,6 +1013,15 @@ def apply_template_placeholders(content: str, note_path: str) -> str:
     now = datetime.now()
     note = Path(note_path)
 
+    def _strftime_sub(match: 're.Match[str]') -> str:
+        fmt = match.group(2)
+        try:
+            return now.strftime(fmt)
+        except (ValueError, TypeError):
+            return match.group(0)
+
+    content = _STRFTIME_PLACEHOLDER_RE.sub(_strftime_sub, content)
+
     replacements = {
         '{{date}}': now.strftime('%Y-%m-%d'),
         '{{time}}': now.strftime('%H:%M:%S'),

documentation/FEATURES.md

@@ -287,6 +287,7 @@ Create notes from reusable templates with dynamic placeholder replacement.
 - `{{day}}` - Current day (DD)
 - `{{title}}` - Note name (without extension)
 - `{{folder}}` - Parent folder name
+- `{{date:FORMAT}}` / `{{time:FORMAT}}` / `{{datetime:FORMAT}}` - Custom format using any Python `strftime()` string, e.g. `{{datetime:%Y%m%d%H%M%S}}` → `20251126143045`. See [Templates](TEMPLATES.md#custom-datetime-formats) for the full recipe list.
 
 ### Example Template
 ```markdown

documentation/TEMPLATES.md

@@ -46,6 +46,39 @@ Templates support dynamic placeholders that are replaced when you create a note:
 | `{{title}}` | Note name (without .md) | `Weekly Meeting` |
 | `{{folder}}` | Parent folder name | `Projects` |
 
+### Custom date/time formats
+
+Need a different format than the defaults above? Any of the three
+date/time placeholders — `{{date}}`, `{{time}}`, `{{datetime}}` — accepts
+an optional `:FORMAT` suffix to override its default format. `FORMAT` is
+any [Python `strftime()` format string](https://docs.python.org/3/library/datetime.html#strftime-and-strptime-format-codes),
+so anything `strftime` can do, your template can do.
+
+> **One rule to remember:** pick the prefix whose default already covers
+> the components you want to format. Use `{{date:…}}` for date-only
+> formats, `{{time:…}}` for time-only formats, and `{{datetime:…}}` when
+> you need both.
+
+#### Common recipes
+
+| Template | Result | Use case |
+|---|---|---|
+| `{{date:%Y%m%d}}` | `20251126` | Date stamp for filenames |
+| `{{time:%H%M%S}}` | `143045` | Time stamp for filenames |
+| `{{datetime:%Y%m%d%H%M%S}}` | `20251126143045` | Sortable, filename-safe full stamp |
+| `{{datetime:%Y%m%dT%H%M%S}}` | `20251126T143045` | ISO-8601 basic, no separators |
+| `{{datetime:%Y-%m-%dT%H:%M:%S}}` | `2025-11-26T14:30:45` | ISO-8601 extended |
+| `{{date:%d/%m/%Y}}` | `26/11/2025` | European-style date |
+| `{{date:%m/%d/%Y}}` | `11/26/2025` | US-style date |
+| `{{date:%A}}` | `Wednesday` | Full weekday name |
+| `{{date:%a}}` | `Wed` | Short weekday name |
+| `{{date:%B}}` | `November` | Full month name |
+| `{{date:%V}}` | `48` | ISO week number |
+| `{{date:%j}}` | `330` | Day of year (1–366) |
+
+> Invalid format strings (typos) are left in the output unchanged so the
+> mistake is visible rather than silently swallowed.
+
 ### Example Template
 
 ```markdown