Fix naturalday/naturaldate wrong answer for tz-aware datetimes

src/humanize/time.py

@@ -318,6 +318,10 @@ def naturalday(value: dt.date | dt.datetime, format: str = "%b %d") -> str:
     """
     import datetime as dt
 
+    # Capture timezone before converting to a plain date so we can
+    # derive "today" in the same timezone as the input value.
+    tzinfo = getattr(value, "tzinfo", None)
+
     try:
         value = dt.date(value.year, value.month, value.day)
     except AttributeError:
@@ -326,7 +330,12 @@ def naturalday(value: dt.date | dt.datetime, format: str = "%b %d") -> str:
     except (OverflowError, ValueError):
         # Date arguments out of range
         return str(value)
-    delta = value - dt.date.today()
+
+    if tzinfo is not None:
+        today = dt.datetime.now(tzinfo).date()
+    else:
+        today = dt.date.today()
+    delta = value - today
 
     if delta.days == 0:
         return _("today")
@@ -344,16 +353,25 @@ def naturaldate(value: dt.date | dt.datetime) -> str:
     """Like `naturalday`, but append a year for dates more than ~five months away."""
     import datetime as dt
 
+    # Capture timezone before converting so we derive "today" correctly.
+    tzinfo = getattr(value, "tzinfo", None)
+
     try:
-        value = dt.date(value.year, value.month, value.day)
+        date_value = dt.date(value.year, value.month, value.day)
     except AttributeError:
         # Passed value wasn't date-ish
         return str(value)
     except (OverflowError, ValueError):
         # Date arguments out of range
         return str(value)
-    delta = _abs_timedelta(value - dt.date.today())
+
+    if tzinfo is not None:
+        today = dt.datetime.now(tzinfo).date()
+    else:
+        today = dt.date.today()
+    delta = _abs_timedelta(date_value - today)
     if delta.days >= 5 * 365 / 12:
+        # Pass original value so naturalday() can extract timezone info.
         return naturalday(value, "%b %d %Y")
     return naturalday(value)
 

tests/test_time.py

@@ -300,6 +300,51 @@ def test_naturaldate(test_input: dt.date, expected: str) -> None:
     assert humanize.naturaldate(test_input) == expected
 
 
+@freeze_time("2023-10-15 23:00:00", tz_offset=0)
+def test_naturalday_tz_aware() -> None:
+    """Test that naturalday compares dates in the value's timezone, not system local."""
+    # https://github.com/python-humanize/humanize/issues/152
+    utc = dt.timezone.utc
+    aedt = dt.timezone(dt.timedelta(hours=11))
+    edt = dt.timezone(dt.timedelta(hours=-4))
+    pdt = dt.timezone(dt.timedelta(hours=-7))
+
+    # A moment 7 hours in the future (UTC).
+    future = dt.datetime(2023, 10, 16, hour=6, tzinfo=utc)
+
+    # In UTC: now is Oct 15, future is Oct 16 → tomorrow
+    assert humanize.naturalday(future) == "tomorrow"
+
+    # In AEDT (+11): now is Oct 16 10:00, future is Oct 16 17:00 → today
+    assert humanize.naturalday(future.astimezone(aedt)) == "today"
+
+    # In EDT (-4): now is Oct 15 19:00, future is Oct 16 02:00 → tomorrow
+    assert humanize.naturalday(future.astimezone(edt)) == "tomorrow"
+
+    # In PDT (-7): now is Oct 15 16:00, future is Oct 15 23:00 → today
+    assert humanize.naturalday(future.astimezone(pdt)) == "today"
+
+
+@freeze_time("2023-10-15 23:00:00", tz_offset=0)
+def test_naturaldate_tz_aware() -> None:
+    """Test naturaldate compares dates in value's timezone."""
+    # https://github.com/python-humanize/humanize/issues/152
+    utc = dt.timezone.utc
+    aedt = dt.timezone(dt.timedelta(hours=11))
+    edt = dt.timezone(dt.timedelta(hours=-4))
+
+    future = dt.datetime(2023, 10, 16, hour=6, tzinfo=utc)
+
+    # In UTC: tomorrow
+    assert humanize.naturaldate(future) == "tomorrow"
+
+    # In AEDT (+11): today
+    assert humanize.naturaldate(future.astimezone(aedt)) == "today"
+
+    # In EDT (-4): tomorrow
+    assert humanize.naturaldate(future.astimezone(edt)) == "tomorrow"
+
+
 @pytest.mark.parametrize(
     "seconds, expected",
     [