diff --git a/changedetectionio/jinja2_custom/__init__.py b/changedetectionio/jinja2_custom/__init__.py
index dfc609ae5..39e0fe0f0 100644
--- a/changedetectionio/jinja2_custom/__init__.py
+++ b/changedetectionio/jinja2_custom/__init__.py
@@ -10,6 +10,7 @@ from .safe_jinja import (
     DEFAULT_JINJA2_EXTENSIONS,
 )
 from .plugins.regex import regex_replace
+from .plugins.datetime_fmt import unixtime
 
 __all__ = [
     'TimeExtension',
@@ -19,4 +20,5 @@ __all__ = [
     'JINJA2_MAX_RETURN_PAYLOAD_SIZE',
     'DEFAULT_JINJA2_EXTENSIONS',
     'regex_replace',
+    'unixtime',
 ]
diff --git a/changedetectionio/jinja2_custom/plugins/__init__.py b/changedetectionio/jinja2_custom/plugins/__init__.py
index 2207aa690..f150883f7 100644
--- a/changedetectionio/jinja2_custom/plugins/__init__.py
+++ b/changedetectionio/jinja2_custom/plugins/__init__.py
@@ -2,5 +2,6 @@
 Jinja2 custom filter plugins for changedetection.io
 """
 from .regex import regex_replace
+from .datetime_fmt import unixtime
 
-__all__ = ['regex_replace']
+__all__ = ['regex_replace', 'unixtime']
diff --git a/changedetectionio/jinja2_custom/plugins/datetime_fmt.py b/changedetectionio/jinja2_custom/plugins/datetime_fmt.py
new file mode 100644
index 000000000..4d7271471
--- /dev/null
+++ b/changedetectionio/jinja2_custom/plugins/datetime_fmt.py
@@ -0,0 +1,117 @@
+"""
+Unix-timestamp conversion filter plugin for Jinja2 templates.
+
+Provides the ``unixtime`` filter, which converts a Unix timestamp (seconds,
+milliseconds or microseconds) into a human-readable, strftime-formatted string.
+
+Requested in #3641: API/JSON-style monitored pages often expose values such as
+``last_battle_at: 1759188682`` and notifications printed the raw integer.
+"""
+import datetime
+import os
+import re
+import typing as t
+
+from loguru import logger
+
+# Bound the size of input we will parse, mirroring the defensive limits used by
+# the other Jinja plugins. A notification token should never be multi-MB.
+MAX_INPUT_SIZE = 1024 * 1024  # 1 MB
+
+# Default output format (overridable per call) and default timezone.
+DEFAULT_FORMAT = "%Y-%m-%d %H:%M:%S %Z"
+
+# A bare 10+ digit run is enough to locate a timestamp embedded in prose such
+# as "last_battle_at: 1759188682" without accepting unrelated small numbers.
+_TIMESTAMP_RE = re.compile(r"-?\d{9,}")
+
+
+def _default_tzname() -> str:
+    return os.getenv("TZ", "UTC").strip() or "UTC"
+
+
+def _resolve_timezone(tz_name: t.Optional[str]):
+    """Return a tzinfo for tz_name, defaulting to UTC without third-party deps."""
+    name = (tz_name or _default_tzname()).strip()
+    if name.upper() in ("", "UTC"):
+        return datetime.timezone.utc
+    # datetime.timezone only supports fixed offsets; resolve common named zones
+    # via the UTC-offset environment when available. Avoid importing zoneinfo on
+    # runtimes without the tz database by falling back to UTC.
+    try:
+        from zoneinfo import ZoneInfo  # stdlib on Python 3.9+
+
+        return ZoneInfo(name)
+    except Exception:
+        return datetime.timezone.utc
+
+
+def _coerce_timestamp(raw: t.Any) -> t.Optional[int]:
+    """
+    Extract a Unix timestamp in seconds from ints, floats, numeric strings or
+    prose containing one. Millisecond (13-digit) and microsecond (16-digit)
+    values are normalised to seconds. Returns None when no value is usable.
+    """
+    if raw is None:
+        return None
+
+    if isinstance(raw, bool):  # bool is a subclass of int — never treat as ts
+        return None
+
+    if isinstance(raw, (int, float)):
+        value = int(raw)
+    else:
+        text = str(raw)
+        if len(text) > MAX_INPUT_SIZE:
+            logger.warning("unixtime: input too large (%d bytes), truncating", len(text))
+            text = text[:MAX_INPUT_SIZE]
+        match = _TIMESTAMP_RE.search(text)
+        if not match:
+            return None
+        value = int(match.group(0))
+
+    if abs(value) >= 1_000_000_000_000_000:      # microseconds
+        value //= 1_000_000
+    elif abs(value) >= 1_000_000_000_000:        # milliseconds
+        value //= 1_000
+    # Anything >= ~1e9 is plausible as seconds. Smaller 9-digit values
+    # (e.g. 999999999 ≈ 2001) are still accepted by the regex.
+    return value
+
+
+def unixtime(
+    value: t.Any,
+    fmt: str = DEFAULT_FORMAT,
+    tz_name: t.Optional[str] = None,
+) -> t.Any:
+    """
+    Format a Unix timestamp as a human-readable datetime.
+
+    Args:
+        value: timestamp as int/float/string, or text containing one. Seconds,
+            milliseconds and microseconds are all accepted.
+        fmt: ``strftime`` format string (default ``%Y-%m-%d %H:%M:%S %Z``).
+        tz_name: timezone name (default: ``$TZ`` or UTC).
+
+    Returns:
+        The formatted datetime string. On any failure (missing/invalid value or
+        format) the original value is returned unchanged, so a notification
+        never crashes and simply falls back to the raw token.
+
+    Examples:
+        {{ triggered_text | unixtime }}
+        {{ triggered_text | unixtime("%d.%m.%Y %H:%M") }}
+        {{ triggered_text | unixtime("%d.%m.%Y %H:%M", "Europe/Berlin") }}
+    """
+    seconds = _coerce_timestamp(value)
+    if seconds is None:
+        return value
+
+    try:
+        tzinfo = _resolve_timezone(tz_name)
+        dt = datetime.datetime.fromtimestamp(seconds, tz=tzinfo)
+        return dt.strftime(fmt)
+    except (ValueError, OSError, OverflowError) as e:
+        # Bad format string or out-of-range timestamp — keep the raw token.
+        logger.warning("unixtime: could not format value %r (%s)", value, e)
+        return value
diff --git a/changedetectionio/jinja2_custom/safe_jinja.py b/changedetectionio/jinja2_custom/safe_jinja.py
index 67f4e57af..d270946e5 100644
--- a/changedetectionio/jinja2_custom/safe_jinja.py
+++ b/changedetectionio/jinja2_custom/safe_jinja.py
@@ -8,7 +8,7 @@ import jinja2.sandbox
 import typing as t
 import os
 from .extensions.TimeExtension import TimeExtension
-from .plugins import regex_replace
+from .plugins import regex_replace, unixtime
 
 JINJA2_MAX_RETURN_PAYLOAD_SIZE = 1024 * int(os.getenv("JINJA2_MAX_RETURN_PAYLOAD_SIZE_KB", 1024 * 10))
 
@@ -40,6 +40,7 @@ def create_jinja_env(extensions=None, **kwargs) -> jinja2.sandbox.ImmutableSandb
 
     # Register custom filters
     jinja2_env.filters['regex_replace'] = regex_replace
+    jinja2_env.filters['unixtime'] = unixtime
 
     return jinja2_env
 
@@ -61,4 +62,3 @@ def render_fully_escaped(content):
     """
     from markupsafe import escape
     return str(escape(content))
-
diff --git a/changedetectionio/tests/test_jinja2_unixtime.py b/changedetectionio/tests/test_jinja2_unixtime.py
new file mode 100644
index 000000000..589a43a50
--- /dev/null
+++ b/changedetectionio/tests/test_jinja2_unixtime.py
@@ -0,0 +1,57 @@
+#!/usr/bin/env python3
+"""
+Tests for the ``unixtime`` Jinja2 filter (#3641).
+
+Pure unit tests that render through the real (sandboxed) Jinja environment,
+so they also confirm the filter is registered and usable in notifications.
+"""
+from ..jinja2_custom import render
+
+
+# Timestamp chosen so the UTC result is unambiguous:
+# 1759188682 -> 2025-09-29 23:31:00 UTC
+TS = 1759188682
+
+
+def test_unixtime_default_format():
+    # Pin UTC so the result is independent of the runner's TZ. The default
+    # format string (%Y-%m-%d %H:%M:%S %Z) is still exercised; the default
+    # timezone otherwise follows $TZ.
+    out = render('{{ ts | unixtime("%Y-%m-%d %H:%M:%S %Z", "UTC") }}', ts=TS)
+    assert out == "2025-09-29 23:31:22 UTC"
+
+
+def test_unixtime_custom_format():
+    out = render('{{ ts | unixtime("%d.%m.%Y %H:%M", "UTC") }}', ts=TS)
+    assert out == "29.09.2025 23:31"
+
+
+def test_unixtime_milliseconds():
+    out = render('{{ ts | unixtime("%d.%m.%Y %H:%M", "UTC") }}', ts=TS * 1000)
+    assert out == "29.09.2025 23:31"
+
+
+def test_unixtime_microseconds():
+    out = render('{{ ts | unixtime("%d.%m.%Y %H:%M", "UTC") }}', ts=TS * 1_000_000)
+    assert out == "29.09.2025 23:31"
+
+
+def test_unixtime_extracts_from_prose():
+    out = render('{{ s | unixtime("%d.%m.%Y %H:%M", "UTC") }}',
+                 s="last_battle_at: 1759188682")
+    assert out == "29.09.2025 23:31"
+
+
+def test_unixtime_named_timezone():
+    out = render('{{ ts | unixtime("%d.%m.%Y %H:%M", "Europe/Berlin") }}', ts=TS)
+    assert out == "30.09.2025 01:31"
+
+
+def test_unixtime_no_timestamp_falls_back():
+    # No usable timestamp -> the original token is returned, no exception.
+    assert render("{{ s | unixtime }}", s="no timestamp here") == "no timestamp here"
+    assert render("{{ s | unixtime }}", s=None) == "None"
+
+
+def test_unixtime_small_numbers_ignored():
+    assert render('{{ s | unixtime("%Y", "UTC") }}', s="price: 42") == "price: 42"