Fix instance() ignoring the tz argument for aware datetimes

src/pendulum/__init__.py

@@ -201,32 +201,38 @@ def time(hour: int, minute: int = 0, second: int = 0, microsecond: int = 0) -> T
 @overload
 def instance(
     obj: _datetime.datetime,
-    tz: str | Timezone | FixedTimezone | _datetime.tzinfo | None = UTC,
+    tz: str | Timezone | FixedTimezone | _datetime.tzinfo | None = None,
 ) -> DateTime: ...
 
 
 @overload
 def instance(
     obj: _datetime.date,
-    tz: str | Timezone | FixedTimezone | _datetime.tzinfo | None = UTC,
+    tz: str | Timezone | FixedTimezone | _datetime.tzinfo | None = None,
 ) -> Date: ...
 
 
 @overload
 def instance(
     obj: _datetime.time,
-    tz: str | Timezone | FixedTimezone | _datetime.tzinfo | None = UTC,
+    tz: str | Timezone | FixedTimezone | _datetime.tzinfo | None = None,
 ) -> Time: ...
 
 
 def instance(
     obj: _datetime.datetime | _datetime.date | _datetime.time,
-    tz: str | Timezone | FixedTimezone | _datetime.tzinfo | None = UTC,
+    tz: str | Timezone | FixedTimezone | _datetime.tzinfo | None = None,
 ) -> DateTime | Date | Time:
     """
     Create a DateTime/Date/Time instance from a datetime/date/time native one.
     """
-    if isinstance(obj, (DateTime, Date, Time)):
+    if isinstance(obj, DateTime):
+        if tz is not None:
+            return DateTime.instance(obj, tz=tz)
+
+        return obj
+
+    if isinstance(obj, (Date, Time)):
         return obj
 
     if isinstance(obj, _datetime.date) and not isinstance(obj, _datetime.datetime):

src/pendulum/datetime.py

@@ -128,13 +128,19 @@ def create(
     def instance(
         cls,
         dt: datetime.datetime,
-        tz: str | Timezone | FixedTimezone | datetime.tzinfo | None = UTC,
+        tz: str | Timezone | FixedTimezone | datetime.tzinfo | None = None,
     ) -> Self:
-        tz = dt.tzinfo or tz
-
         if tz is not None:
+            # An explicitly given timezone takes precedence over the one
+            # carried by the datetime: aware datetimes are converted to it,
+            # while naive ones are interpreted in it.
             tz = pendulum._safe_timezone(tz, dt=dt)
 
+            if dt.tzinfo is not None:
+                dt = dt.astimezone(tz)
+        else:
+            tz = pendulum._safe_timezone(dt.tzinfo or UTC, dt=dt)
+
         return cls.create(
             dt.year,
             dt.month,
@@ -1256,16 +1262,26 @@ def fromtimestamp(cls, t: float, tz: datetime.tzinfo | None = None) -> Self:
 
     @classmethod
     def utcfromtimestamp(cls, t: float) -> Self:
-        return cls.instance(
-            datetime.datetime.fromtimestamp(t, tz=datetime.timezone.utc).replace(
-                tzinfo=None
-            ),
-            tz=None,
+        dt = datetime.datetime.fromtimestamp(t, tz=datetime.timezone.utc).replace(
+            tzinfo=None
+        )
+
+        return cls(
+            dt.year,
+            dt.month,
+            dt.day,
+            dt.hour,
+            dt.minute,
+            dt.second,
+            dt.microsecond,
+            fold=dt.fold,
         )
 
     @classmethod
     def fromordinal(cls, n: int) -> Self:
-        return cls.instance(datetime.datetime.fromordinal(n), tz=None)
+        dt = datetime.datetime.fromordinal(n)
+
+        return cls(dt.year, dt.month, dt.day)
 
     @classmethod
     def combine(
@@ -1274,7 +1290,33 @@ def combine(
         time: datetime.time,
         tzinfo: datetime.tzinfo | None = None,
     ) -> Self:
-        return cls.instance(datetime.datetime.combine(date, time), tz=tzinfo)
+        dt = datetime.datetime.combine(date, time)
+
+        tz = tzinfo if tzinfo is not None else dt.tzinfo
+
+        if tz is None:
+            return cls(
+                dt.year,
+                dt.month,
+                dt.day,
+                dt.hour,
+                dt.minute,
+                dt.second,
+                dt.microsecond,
+                fold=dt.fold,
+            )
+
+        return cls.create(
+            dt.year,
+            dt.month,
+            dt.day,
+            dt.hour,
+            dt.minute,
+            dt.second,
+            dt.microsecond,
+            tz=tz,
+            fold=dt.fold,
+        )
 
     def astimezone(self, tz: datetime.tzinfo | None = None) -> Self:
         # Convert a plain datetime: tzinfo.fromutc() implementations add

src/pendulum/parser.py

@@ -75,7 +75,7 @@ def _parse(
             duration = parsed.duration
 
             if parsed.start is not None:
-                dt = pendulum.instance(parsed.start, tz=options.get("tz", UTC))
+                dt = pendulum.instance(parsed.start, tz=options.get("tz"))
 
                 return pendulum.interval(
                     dt,
@@ -92,7 +92,7 @@ def _parse(
                 )
 
             dt = pendulum.instance(
-                t.cast("datetime.datetime", parsed.end), tz=options.get("tz", UTC)
+                t.cast("datetime.datetime", parsed.end), tz=options.get("tz")
             )
 
             return pendulum.interval(
@@ -111,10 +111,10 @@ def _parse(
 
         return pendulum.interval(
             pendulum.instance(
-                t.cast("datetime.datetime", parsed.start), tz=options.get("tz", UTC)
+                t.cast("datetime.datetime", parsed.start), tz=options.get("tz")
             ),
             pendulum.instance(
-                t.cast("datetime.datetime", parsed.end), tz=options.get("tz", UTC)
+                t.cast("datetime.datetime", parsed.end), tz=options.get("tz")
             ),
         )
 

src/pendulum/time.py

@@ -36,12 +36,12 @@ class Time(FormattableMixin, time):
 
     @classmethod
     def instance(
-        cls, t: time, tz: str | Timezone | FixedTimezone | datetime.tzinfo | None = UTC
+        cls, t: time, tz: str | Timezone | FixedTimezone | datetime.tzinfo | None = None
     ) -> Self:
-        tz = t.tzinfo or tz
+        if tz is None:
+            tz = t.tzinfo or UTC
 
-        if tz is not None:
-            tz = pendulum._safe_timezone(tz)
+        tz = pendulum._safe_timezone(tz)
 
         return cls(t.hour, t.minute, t.second, t.microsecond, tzinfo=tz, fold=t.fold)
 

tests/test_main.py

@@ -36,6 +36,42 @@ def test_instance_with_aware_datetime_any_tzinfo() -> None:
     assert now.timezone_name == "+02:00"
 
 
+def test_instance_with_aware_datetime_and_explicit_tz_converts() -> None:
+    dt = datetime(2024, 9, 3, 13, 56, 35, tzinfo=timezone("Europe/Brussels"))
+    now = pendulum.instance(dt, tz="EST")
+
+    assert now.timezone_name == "EST"
+    # 13:56 in Brussels (UTC+2) is 06:56 EST (UTC-5)
+    assert (now.hour, now.minute, now.second) == (6, 56, 35)
+    assert now == dt
+
+
+def test_instance_with_pendulum_datetime_and_explicit_tz_converts() -> None:
+    dt = pendulum.datetime(2024, 9, 3, 13, 56, 35, tz="Europe/Brussels")
+    now = pendulum.instance(dt, tz="EST")
+
+    assert now.timezone_name == "EST"
+    assert (now.hour, now.minute, now.second) == (6, 56, 35)
+    assert now == dt
+
+
+def test_instance_with_naive_datetime_and_explicit_tz() -> None:
+    now = pendulum.instance(datetime(2024, 9, 3, 13, 56, 35), tz="Europe/Paris")
+
+    assert now.timezone_name == "Europe/Paris"
+    assert (now.hour, now.minute, now.second) == (13, 56, 35)
+
+
+def test_datetime_instance_with_explicit_tz_converts() -> None:
+    dt = pendulum.datetime(2024, 9, 3, 13, 56, 35, tz="Europe/Brussels")
+    converted = pendulum.DateTime.instance(dt, tz="America/New_York")
+
+    assert converted.timezone_name == "America/New_York"
+    # 13:56 in Brussels (UTC+2) is 07:56 in New York (UTC-4)
+    assert (converted.hour, converted.minute, converted.second) == (7, 56, 35)
+    assert converted == dt
+
+
 def test_instance_with_date() -> None:
     dt = pendulum.instance(date(2022, 12, 23))