fix: handle negative timestamps in DateTime constructors

Author: parinporecha

src/pendulum/datetime.py

@@ -1253,11 +1253,21 @@ def __radd__(self, other: datetime.timedelta) -> Self:
     def fromtimestamp(cls, t: float, tz: datetime.tzinfo | None = None) -> Self:
         tzinfo = pendulum._safe_timezone(tz)
 
-        return cls.instance(datetime.datetime.fromtimestamp(t, tz=tzinfo), tz=tzinfo)
+        try:
+            dt = datetime.datetime.fromtimestamp(t, tz=tzinfo)
+        except OSError:
+            dt = (cls._EPOCH + datetime.timedelta(seconds=t)).astimezone(tzinfo)
+
+        return cls.instance(dt, tz=tzinfo)
 
     @classmethod
     def utcfromtimestamp(cls, t: float) -> Self:
-        return cls.instance(datetime.datetime.utcfromtimestamp(t), tz=None)
+        try:
+            dt = datetime.datetime.utcfromtimestamp(t)
+        except OSError:
+            dt = datetime.datetime(1970, 1, 1) + datetime.timedelta(seconds=t)
+
+        return cls.instance(dt, tz=None)
 
     @classmethod
     def fromordinal(cls, n: int) -> Self:

tests/datetime/test_behavior.py

@@ -1,6 +1,9 @@
 from __future__ import annotations
 
+import datetime as datetime_
+import importlib
 import pickle
+import types
 import zoneinfo
 
 from copy import deepcopy
@@ -107,6 +110,52 @@ def test_utcfromtimestamp():
     assert p == dt
 
 
+def test_fromtimestamp_falls_back_for_negative_timestamp(monkeypatch):
+    pendulum_datetime_module = importlib.import_module("pendulum.datetime")
+
+    class FakeDateTime(datetime_.datetime):
+        @classmethod
+        def fromtimestamp(cls, t: float, tz: datetime_.tzinfo | None = None):
+            if t == -43201:
+                raise OSError("Invalid argument")
+
+            return super().fromtimestamp(t, tz=tz)
+
+    monkeypatch.setattr(
+        pendulum_datetime_module,
+        "datetime",
+        types.SimpleNamespace(datetime=FakeDateTime, timedelta=datetime_.timedelta),
+    )
+
+    p = pendulum.DateTime.fromtimestamp(-43201, pendulum.UTC)
+
+    assert p == pendulum.datetime(1969, 12, 31, 11, 59, 59)
+    assert p.timezone_name == "UTC"
+
+
+def test_utcfromtimestamp_falls_back_for_negative_timestamp(monkeypatch):
+    pendulum_datetime_module = importlib.import_module("pendulum.datetime")
+
+    class FakeDateTime(datetime_.datetime):
+        @classmethod
+        def utcfromtimestamp(cls, t: float):
+            if t == -43201:
+                raise OSError("Invalid argument")
+
+            return super().utcfromtimestamp(t)
+
+    monkeypatch.setattr(
+        pendulum_datetime_module,
+        "datetime",
+        types.SimpleNamespace(datetime=FakeDateTime, timedelta=datetime_.timedelta),
+    )
+
+    p = pendulum.DateTime.utcfromtimestamp(-43201)
+
+    assert p == pendulum.naive(1969, 12, 31, 11, 59, 59)
+    assert p.tzinfo is None
+
+
 def test_fromordinal():
     assert datetime.fromordinal(730120) == pendulum.DateTime.fromordinal(730120)