diff --git a/picard/util/__init__.py b/picard/util/__init__.py
index 739ee1647b..24cfd4e586 100644
--- a/picard/util/__init__.py
+++ b/picard/util/__init__.py
@@ -85,6 +85,7 @@
     gettext as _,
     gettext_constants,
 )
+from picard.util.datestr_util import sanitize_date  # noqa: F401
 
 
 winreg = None
@@ -323,29 +324,6 @@ def format_time(ms, display_zero=False):
         return "%d:%02d:%02d" % (hours, minutes, seconds)
 
 
-def sanitize_date(datestr):
-    """Sanitize date format.
-
-    e.g.: "1980-00-00" -> "1980"
-          "1980-  -  " -> "1980"
-          "1980-00-23" -> "1980-00-23"
-          ...
-    """
-    date = []
-    for num in reversed(datestr.split("-")):
-        try:
-            num = int(num.strip())
-        except ValueError:
-            if num == '':
-                num = 0
-            else:
-                break
-        if num or (num == 0 and date):
-            date.append(num)
-    date.reverse()
-    return ("", "%04d", "%04d-%02d", "%04d-%02d-%02d")[len(date)] % tuple(date)
-
-
 def replace_win32_incompat(string, repl="_", replacements=None):  # noqa: E302
     """Replace win32 filename incompatible characters from ``string`` by
     ``repl``."""
diff --git a/picard/util/datestr_util.py b/picard/util/datestr_util.py
new file mode 100644
index 0000000000..1277860a02
--- /dev/null
+++ b/picard/util/datestr_util.py
@@ -0,0 +1,248 @@
+# -*- coding: utf-8 -*-
+#
+# Picard, the next-generation MusicBrainz tagger
+#
+# Copyright (C) 2025 The MusicBrainz Team
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation; either version 2
+# of the License, or (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+
+"""Utility functions for date str/obj."""
+
+import re
+
+
+def _int_or_none(value: str) -> int | None:
+    value = value.strip()
+    if value == "":
+        return 0
+    try:
+        return int(value)
+    except ValueError:
+        return None
+
+
+def _clamp_year(value: int | None) -> int | None:
+    if value is None:
+        return None
+    if value < 0:
+        return None
+    if value > 9999:
+        return None
+    return value
+
+
+def _is_valid_month(value: int) -> bool:
+    return 0 <= value <= 12
+
+
+def _is_valid_day(value: int) -> bool:
+    return 0 <= value <= 31
+
+
+def _parse_pure_year(value: str) -> str | None:
+    m = re.fullmatch(r"(\d{4})", value)
+    if not m:
+        return None
+    year = _clamp_year(int(m.group(1)))
+    if year in (None, 0):
+        return ""
+    return f"{year:04d}"
+
+
+def _format_from_components(year: int | None, month: int | None, day: int | None) -> str:
+    y = _clamp_year(year if year is not None else -1)
+    if y is None:
+        return ""
+    # y could be 0 here for partial unknown dates; treat specially below
+    if month is None and day is None:
+        return "" if y == 0 else f"{y:04d}"
+
+    m = month if month is not None else 0
+    d = day if day is not None else 0
+    if not _is_valid_month(m) or not _is_valid_day(d):
+        return ""
+
+    if d == 0:
+        if m == 0:
+            return "" if y == 0 else f"{y:04d}"
+        return f"{y:04d}-{m:02d}"
+
+    if m == 0:
+        return f"{y:04d}-00-{d:02d}"
+
+    return f"{y:04d}-{m:02d}-{d:02d}"
+
+
+def _parse_iso_like(value: str) -> str | None:
+    if "-" not in value:
+        return None
+    parts = value.split("-")
+    if not (1 <= len(parts) <= 3):
+        return None
+
+    parsed: list[int] = []
+    for part in reversed(parts):
+        num = _int_or_none(part)
+        if num is None:
+            return None
+        if num or (num == 0 and parsed):
+            parsed.append(num)
+    parsed.reverse()
+
+    if len(parsed) == 1:
+        return _format_from_components(parsed[0], None, None)
+    if len(parsed) == 2:
+        y, m = parsed
+        return _format_from_components(y, m, None)
+    if len(parsed) == 3:
+        y, m, d = parsed
+        # Handle swapped middle and last if clearly YYYY-DD-MM
+        if m > 12 and d <= 12:
+            m, d = d, m
+        return _format_from_components(y, m, d)
+    return None
+
+
+def _parse_slash_separated(value: str) -> str | None:
+    # We only expect 3 tokens (two slashes)
+    try:
+        tokens = value.split("/", 2)
+        a = _int_or_none(tokens[0])
+        b = _int_or_none(tokens[1])
+        c = _int_or_none(tokens[2])
+    except IndexError:
+        return None
+
+    if a is None or b is None or c is None or not (0 < c <= 9999):
+        return None
+    y = _clamp_year(c) or None
+    if y is None:
+        return ""
+    if a > 12 and _is_valid_month(b) and _is_valid_day(a):
+        d, m = a, b
+    elif b > 12 and _is_valid_month(a) and _is_valid_day(b):
+        m, d = a, b
+    else:
+        return None
+    if not _is_valid_month(m) or not _is_valid_day(d) or m == 0:
+        return ""
+    if d == 0:
+        return f"{y:04d}-{m:02d}"
+    return f"{y:04d}-{m:02d}-{d:02d}"
+
+
+def _parse_compact_eight(value: str) -> str | None:
+    m = re.fullmatch(r"(\d{4})(\d{2})(\d{2})", value)
+    if not m:
+        return None
+
+    y = _clamp_year(int(m.group(1)))
+    if y is None:
+        return ""
+
+    a = int(m.group(2))
+    b = int(m.group(3))
+    if _is_valid_month(a) and _is_valid_day(b) and a != 0:
+        return f"{y:04d}-{a:02d}-{b:02d}"
+    if _is_valid_month(b) and _is_valid_day(a) and b != 0:
+        return f"{y:04d}-{b:02d}-{a:02d}"
+    if a == 0 and _is_valid_day(b):
+        return f"{y:04d}"
+    if _is_valid_month(a) and b == 0:
+        if a == 0:
+            return f"{y:04d}"
+        return f"{y:04d}-{a:02d}"
+    return ""
+
+
+def sanitize_date(datestr: str, disable_sanitization: bool = False) -> str:
+    """Normalize a date string with optional sanitization bypass.
+
+    Parameters
+    ----------
+    datestr : str
+        Raw date string to normalize. Supported inputs include:
+        - "YYYY", "YYYY-MM", "YYYY-MM-DD"
+        - "YYYY-DD-MM" (normalized to "YYYY-MM-DD" when unambiguous)
+        - "DD/MM/YYYY" and "MM/DD/YYYY" (disambiguated heuristically)
+        - "YYYYMMDD" and "YYYYDDMM"
+        Unknown components may be provided as "00" (or left empty for
+        hyphenated inputs, e.g. "2006--"), meaning the component is unknown.
+    disable_sanitization : bool, default False
+        If True, returns the input unchanged.
+
+    Returns
+    -------
+    str
+        Normalized date in one of: "YYYY", "YYYY-MM", or "YYYY-MM-DD".
+        Returns an empty string if the input cannot be normalized when
+        sanitization is enabled.
+
+    Notes
+    -----
+    - Unknown components are preserved without shifting other components.
+      For example, month "00" with a known day stays as month "00":
+      "2005-00-12" -> "2005-00-12" (not "2005-12").
+    - Day "00" drops the day component: "2005-12-00" -> "2005-12".
+    - Month "00" drops only the month when no day is given: "2005-00" -> "2005".
+    - Fully unknown date "0000-00-00" normalizes to an empty string, but
+      partially unknown values such as "0000-00-23" are preserved.
+
+    Examples
+    --------
+    >>> sanitize_date('2005-12-00')
+    '2005-12'
+    >>> sanitize_date('2005-00-12')
+    '2005-00-12'
+    >>> sanitize_date('31/12/2005')
+    '2005-12-31'
+    >>> sanitize_date('20051231')
+    '2005-12-31'
+    >>> sanitize_date('20053112')
+    '2005-12-31'
+    >>> sanitize_date('2006--')
+    '2006'
+    """
+    if disable_sanitization:
+        return datestr
+
+    if not datestr or not isinstance(datestr, str):
+        return ""
+
+    value = datestr.strip()
+    if value == "":
+        return ""
+
+    # 1) Pure year
+    result = _parse_pure_year(value)
+    if result is not None:
+        return result
+
+    # 2) Hyphen-separated ISO-like
+    result = _parse_iso_like(value)
+    if result is not None:
+        return result
+
+    # 3) Slash-separated
+    result = _parse_slash_separated(value)
+    if result is not None:
+        return result
+
+    # 4) Compact YYYYMMDD or YYYYDDMM
+    result = _parse_compact_eight(value)
+    if result is not None:
+        return result
+
+    return ""
diff --git a/test/test_dateutil_normalize.py b/test/test_dateutil_normalize.py
new file mode 100644
index 0000000000..cbe28e0166
--- /dev/null
+++ b/test/test_dateutil_normalize.py
@@ -0,0 +1,108 @@
+# -*- coding: utf-8 -*-
+#
+# Picard, the next-generation MusicBrainz tagger
+#
+# Copyright (C) 2025 The MusicBrainz Team
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation; either version 2
+# of the License, or (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+
+"""Test sanitize_date function."""
+
+from collections.abc import Callable
+
+from picard.util import sanitize_date
+
+import pytest
+
+
+@pytest.fixture
+def norm() -> Callable[[str], str]:
+    return sanitize_date
+
+
+@pytest.mark.parametrize(
+    ("src", "expected"),
+    [
+        ("", ""),
+        ("0", ""),
+        ("0000", ""),
+        ("2006", "2006"),
+        ("2006--", "2006"),
+        ("2006-00-02", "2006-00-02"),
+        ("2006   ", "2006"),
+        ("2006 02", ""),
+        ("2006.02", ""),
+        ("2006-02", "2006-02"),
+        ("2006-02-00", "2006-02"),
+        ("2006-00-00", "2006"),
+        ("2006-02-23", "2006-02-23"),
+        ("2006-00-23", "2006-00-23"),
+        ("0000-00-23", "0000-00-23"),
+        ("0000-02", "0000-02"),
+        ("--23", "0000-00-23"),
+    ],
+)
+def test_sanitize_date_basic(norm: Callable, src: str, expected: str) -> None:
+    assert norm(src) == expected
+
+
+@pytest.mark.parametrize(
+    ("src", "expected"),
+    [
+        ("2005-12-00", "2005-12"),
+        ("2005-00-12", "2005-00-12"),  # bugfix: don't shift 00 month
+        ("0000-00-12", "0000-00-12"),  # bugfix: don't become 0012
+        ("0000-00-00", ""),
+    ],
+)
+def test_sanitize_date_bug_cases(norm: Callable, src: str, expected: str) -> None:
+    assert norm(src) == expected
+
+
+@pytest.mark.parametrize(
+    ("src", "expected"),
+    [
+        ("31/12/2005", "2005-12-31"),
+        ("12/31/2005", "2005-12-31"),
+        ("20051231", "2005-12-31"),
+        ("20053112", "2005-12-31"),
+    ],
+)
+def test_sanitize_date_other_formats(norm: Callable, src: str, expected: str) -> None:
+    assert norm(src) == expected
+
+
+@pytest.mark.parametrize(
+    "src",
+    [
+        ("nonsense",),
+        ("2006/13/01",),
+        ("2006-13-01",),
+    ],
+)
+def test_sanitize_date_invalid(norm: Callable, src: str) -> None:
+    assert norm(src) == ""
+
+
+@pytest.mark.parametrize(
+    "src",
+    [
+        "0000-00-00",
+        "2005-00-12",
+        "2005-12-00",
+    ],
+)
+def test_disable_sanitization_returns_input(src: str) -> None:
+    assert sanitize_date(src, disable_sanitization=True) == src