Preserve fixed-width year formatting tokens

Author: FanWu-ai

docs/docs/string_formatting.md

@@ -106,9 +106,9 @@ The following tokens are currently supported:
 
 |                                | Token         | Output                                     |
 | ------------------------------ | ------------- | ------------------------------------------ |
-| **Year**                       | YYYY          | 2000, 2001, 2002 ... 2012, 2013            |
+| **Year**                       | YYYY          | 0001, 0002 ... 2000, 2001 ... 9999          |
 |                                | YY            | 00, 01, 02 ... 12, 13                      |
-|                                | Y             | 2000, 2001, 2002 ... 2012, 2013            |
+|                                | Y             | 1, 2 ... 2000, 2001 ... 9999                |
 | **Quarter**                    | Q             | 1 2 3 4                                    |
 |                                | Qo            | 1st 2nd 3rd 4th                            |
 | **Month**                      | MMMM          | January, February, March ...               |

src/pendulum/formatting/formatter.py

@@ -99,8 +99,8 @@ class Formatter:
 
     _TOKENS_RULES: ClassVar[dict[str, Callable[[pendulum.DateTime], str]]] = {
         # Year
-        "YYYY": lambda dt: f"{dt.year:d}",
-        "YY": lambda dt: f"{dt.year:d}"[2:],
+        "YYYY": lambda dt: f"{dt.year:04d}",
+        "YY": lambda dt: f"{dt.year % 100:02d}",
         "Y": lambda dt: f"{dt.year:d}",
         # Quarter
         "Q": lambda dt: f"{dt.quarter:d}",

tests/formatting/test_year_padding_regression.py

@@ -0,0 +1,36 @@
+from __future__ import annotations
+
+import pytest
+
+import pendulum
+
+from pendulum.formatting import Formatter
+
+
+@pytest.mark.parametrize(
+    "year, full, short",
+    [
+        (1, "0001", "01"),
+        (9, "0009", "09"),
+        (10, "0010", "10"),
+        (99, "0099", "99"),
+        (100, "0100", "00"),
+        (101, "0101", "01"),
+        (999, "0999", "99"),
+        (1000, "1000", "00"),
+        (2009, "2009", "09"),
+        (9999, "9999", "99"),
+    ],
+)
+def test_year_tokens_have_fixed_width(year: int, full: str, short: str) -> None:
+    value = pendulum.datetime(year, 3, 14)
+    assert Formatter().format(value, "YYYY YY Y") == f"{full} {short} {year}"
+    assert value.format("YYYY-MM-DD") == f"{full}-03-14"
+    assert value.format("YY-MM-DD") == f"{short}-03-14"
+    assert pendulum.from_format(value.format("YYYY-MM-DD"), "YYYY-MM-DD") == value
+
+
+def test_year_padding_applies_to_localized_long_formats() -> None:
+    value = pendulum.datetime(42, 3, 14)
+    assert value.format("L", locale="en") == "03/14/0042"
+    assert value.format("[YYYY] YYYY [YY] YY [Y] Y") == "YYYY 0042 YY 42 Y 42"