fix: handle tz-aware datetimes in naturalday and naturaldate

When a tz-aware datetime is passed to naturalday() or naturaldate(),
the date comparison should use 'today' in the datetime's timezone
rather than the system's local date.

Previously the timezone was stripped and the date compared against
dt.date.today(), which could yield wrong results (e.g. returning
'tomorrow' when the local date in the given timezone is actually
the same day).

Fixes #152

Author: bysiber

src/humanize/time.py

@@ -319,14 +319,20 @@ def naturalday(value: dt.date | dt.datetime, format: str = "%b %d") -> str:
     import datetime as dt
 
     try:
+        # When value is a tz-aware datetime, compute "today" in that timezone
+        # so the comparison uses the correct local date.
+        if isinstance(value, dt.datetime) and value.tzinfo is not None:
+            today = dt.datetime.now(value.tzinfo).date()
+        else:
+            today = dt.date.today()
         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 = value - dt.date.today()
+    delta = value - today
 
     if delta.days == 0:
         return _("today")
@@ -344,18 +350,23 @@ 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
 
+    original_value = value
     try:
+        if isinstance(value, dt.datetime) and value.tzinfo is not None:
+            today = dt.datetime.now(value.tzinfo).date()
+        else:
+            today = dt.date.today()
         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())
+    delta = _abs_timedelta(value - today)
     if delta.days >= 5 * 365 / 12:
-        return naturalday(value, "%b %d %Y")
-    return naturalday(value)
+        return naturalday(original_value, "%b %d %Y")
+    return naturalday(original_value)
 
 
 def _quotient_and_remainder(

tests/test_time.py

@@ -300,6 +300,32 @@ def test_naturaldate(test_input: dt.date, expected: str) -> None:
     assert humanize.naturaldate(test_input) == expected
 
 
+@freeze_time("2023-10-15 23:00:00+00:00")
+def test_naturaldate_tz_aware() -> None:
+    """naturaldate should compare dates in the timezone of the given value."""
+    utc = dt.timezone.utc
+    aedt = dt.timezone(dt.timedelta(hours=11))
+    cest = dt.timezone(dt.timedelta(hours=2))
+    edt = dt.timezone(dt.timedelta(hours=-4))
+    pdt = dt.timezone(dt.timedelta(hours=-7))
+    future = dt.datetime(2023, 10, 16, hour=6, tzinfo=utc)
+
+    # UTC: now is Oct 15, future is Oct 16 => tomorrow
+    assert humanize.naturaldate(future) == "tomorrow"
+
+    # AEDT (+11): now is Oct 16 10:00, future is Oct 16 17:00 => today
+    assert humanize.naturaldate(future.astimezone(aedt)) == "today"
+
+    # CEST (+2): now is Oct 16 01:00, future is Oct 16 08:00 => today
+    assert humanize.naturaldate(future.astimezone(cest)) == "today"
+
+    # EDT (-4): now is Oct 15 19:00, future is Oct 16 02:00 => tomorrow
+    assert humanize.naturaldate(future.astimezone(edt)) == "tomorrow"
+
+    # PDT (-7): now is Oct 15 16:00, future is Oct 15 23:00 => today
+    assert humanize.naturaldate(future.astimezone(pdt)) == "today"
+
+
 @pytest.mark.parametrize(
     "seconds, expected",
     [