Fix naturalday/naturaldate giving wrong answer for tz-aware datetimes

When a tz-aware datetime is passed, naturalday() and naturaldate()
extract the date in the value's timezone but compare it with
date.today() which uses system local time. This produces wrong results
when the value's timezone differs from the system timezone.

Fix: capture the value's tzinfo before converting to a plain date,
then derive "today" via datetime.now(tzinfo).date() so both dates
are in the same timezone.

Fixes #152

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: worksbyfriday

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 that naturaldate 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))
+
+    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",
     [