diff --git a/borax/calendars/festivals2.py b/borax/calendars/festivals2.py
index 7033bf6..9c29e6d 100644
--- a/borax/calendars/festivals2.py
+++ b/borax/calendars/festivals2.py
@@ -17,7 +17,7 @@
     'FreqConst', 'Festival', 'FestivalSchema',
     'SolarFestival', 'LunarFestival', 'WeekFestival', 'TermFestival',
     'encode', 'decode', 'decode_festival',
-    'FestivalLibrary',
+    'FestivalLibrary', 'ConditionUtils'
 ]
 
 MixedDate = Union[date, LunarDate]
diff --git a/borax/calendars/lunardate.py b/borax/calendars/lunardate.py
index b2f08b8..c00591d 100644
--- a/borax/calendars/lunardate.py
+++ b/borax/calendars/lunardate.py
@@ -452,8 +452,8 @@ def gz2offset(gz: str) -> int:
             if x % 2 != y % 2:
                 raise ValueError
             return (6 * x - 5 * y) % 60
-        except (TypeError, ValueError):
-            raise ValueError(f'Invalid gz string: {gz}')
+        except (TypeError, ValueError) as e:
+            raise ValueError(f'Invalid gz string: {gz}') from e
 
     @staticmethod
     def offset2gz(offset: int) -> str:
diff --git a/borax/calendars/ui.py b/borax/calendars/ui.py
index fac9451..2a06d70 100644
--- a/borax/calendars/ui.py
+++ b/borax/calendars/ui.py
@@ -51,7 +51,7 @@ def _init_widgets(self):
         bw, bh = 3, 1
         tool_row_no, head_row_no, week_row_no, day_row_no = range(4)
 
-        today_btn = tk.Button(self, text='今日', relief=tk.GROOVE, command=lambda: self._nav_current_month())
+        today_btn = tk.Button(self, text='今日', relief=tk.GROOVE, command=self._nav_current_month)
         today_btn.grid(row=0, column=5, sticky='wens', columnspan=2, pady=4)
         pre_btn = tk.Button(self, text='\u25C4', width=bw, height=bh, command=lambda: self.page_to(-1),
                             relief=tk.GROOVE)
@@ -85,12 +85,12 @@ def _update_calendar_cell_values(self, event=None):
         month = self._v_month.get()
         cell_index = 0
         _mi, _ma, _left_zero = -1, -1, 0
-        for day, text, wd in self._library.iter_month_daytuples(year, month):
+        for day, text, _ in self._library.iter_month_daytuples(year, month):
             if day == 0:
                 day_text = ''
                 _left_zero += int(_mi == -1)
             else:
-                day_text = '{}\n{}'.format(day, text)
+                day_text = f'{day}\n{text}'
                 if day == 1:
                     _mi = cell_index
                 _ma += 1
diff --git a/borax/capp/borax_calendar_app.py b/borax/capp/borax_calendar_app.py
index 8f5ccbe..1ecb020 100644
--- a/borax/capp/borax_calendar_app.py
+++ b/borax/capp/borax_calendar_app.py
@@ -29,7 +29,7 @@
 class WDateVar(tk.StringVar):
 
     def __init__(self, master=None, value=None, name=None, date_fmt='%Y-%m-%d'):
-        tk.Variable.__init__(self, master, value, name)
+        super().__init__(master, value, name)
         self._date_object = None
         self._date_fmt = date_fmt