Clarify existing upper bound behavior of AmbiguousDate.range()

augur/dates/ambiguous_date.py

@@ -49,6 +49,10 @@ def __init__(self, uncertain_date, fmt="%Y-%m-%d", min_max_year=None):
         self.assert_only_less_significant_uncertainty()
 
     def range(self):
+        """Return the range of possible dates defined by the ambiguous date.
+
+        Impose an upper limit of today's date.
+        """
         min_date = tuple_to_date(
             resolve_uncertain_int(self.uncertain_date_components["Y"], "min"),
             resolve_uncertain_int(self.uncertain_date_components["m"], "min"),
@@ -60,6 +64,8 @@ def range(self):
             resolve_uncertain_int(self.uncertain_date_components["m"], "max"),
             resolve_uncertain_int(self.uncertain_date_components["d"], "max"),
         )
+
+        # Limit the max date to be no later than today's date.
         max_date = min(max_date, datetime.date.today())
 
         return (min_date, max_date)

tests/dates/test_dates.py

@@ -50,10 +50,11 @@ def test_get_numerical_date_from_value_ambiguous_month_and_day(self):
 
     @freeze_time("2000-02-20")
     def test_get_numerical_date_from_value_current_day_limit(self):
-        min_date, max_date = dates.get_numerical_date_from_value("2000-02-XX", "%Y-%m-%d")
+        min_date, max_date = dates.get_numerical_date_from_value("2000-03-XX", "%Y-%m-%d")
+        # min_date is not subject to the upper limit
         assert (min_date
-            == pytest.approx(dates.numeric_date(datetime.date(year=2000, month=2, day=1)), abs=1e-3)
-            == pytest.approx(2000.086, abs=1e-3)
+            == pytest.approx(dates.numeric_date(datetime.date(year=2000, month=3, day=1)), abs=1e-3)
+            == pytest.approx(2000.165, abs=1e-3)
         )
         assert (max_date
             == pytest.approx(dates.numeric_date(datetime.date(year=2000, month=2, day=20)), abs=1e-3)