Parse two-digit years relative to today in parse_date

babel/dates.py

@@ -1366,6 +1366,21 @@ class ParseError(ValueError):
     pass
 
 
+def _expand_two_digit_year(year: int) -> int:
+    """Place a two-digit year within 80 years before and 20 years after today.
+
+    This is the rule ICU documents for parsing abbreviated years, see
+    https://unicode-org.github.io/icu-docs/apidoc/released/icu4j/com/ibm/icu/text/SimpleDateFormat.html
+    """
+    this_year = datetime.date.today().year
+    expanded = this_year - this_year % 100 + year
+    if expanded > this_year + 20:
+        return expanded - 100
+    if expanded <= this_year - 80:
+        return expanded + 100
+    return expanded
+
+
 def parse_date(
     string: str,
     locale: Locale | str | None = None,
@@ -1395,6 +1410,9 @@ def parse_date(
     >>> parse_date('01.04.04', locale='de_DE', format='short')
     datetime.date(2004, 4, 1)
 
+    Two-digit years are placed within 80 years before and 20 years after
+    the current year.
+
     :param string: the string containing the date
     :param locale: a `Locale` object or a locale identifier
     :param locale: a `Locale` object or a locale identifier. Defaults to the system time locale.
@@ -1438,7 +1456,7 @@ def parse_date(
     #        names, both in the requested locale, and english
 
     year = numbers[indexes['Y']]
-    year = 2000 + int(year) if len(year) == 2 else int(year)
+    year = _expand_two_digit_year(int(year)) if len(year) == 2 else int(year)
     month = int(numbers[indexes['M']])
     day = int(numbers[indexes['D']])
     if month > 12:

tests/test_dates.py

@@ -700,6 +700,19 @@ def test_parse_date():
     assert dates.parse_date('2004-04-01', locale='sv_SE', format='short') == date(2004, 4, 1)
 
 
+@pytest.mark.parametrize(('today', 'yy', 'expected'), [
+    ('2026-11-09', '99', 1999),
+    ('2026-11-09', '46', 2046),
+    ('2026-11-09', '47', 1947),
+    ('2090-06-01', '05', 2105),
+    ('2090-06-01', '10', 2110),
+    ('2090-06-01', '11', 2011),
+])
+def test_parse_date_two_digit_year(today, yy, expected):
+    with freezegun.freeze_time(today):
+        assert dates.parse_date(f'1/1/{yy}', locale='en_US').year == expected
+
+
 def test_parse_date_custom_format():
     assert dates.parse_date('1.4.2024', format='dd.mm.yyyy') == date(2024, 4, 1)
     assert dates.parse_date('2024.4.1', format='yyyy.mm.dd') == date(2024, 4, 1)