diff --git a/book.py b/book.py
index cb949af..84347c6 100644
--- a/book.py
+++ b/book.py
@@ -11,6 +11,7 @@ from trytond.transaction import Transaction
 from trytond.pool import Pool
 from trytond.report import Report
 from decimal import Decimal
+from datetime import date
 from sql.aggregate import Sum
 from sql.conditionals import Case, Coalesce
 from sql.functions import CurrentDate
@@ -274,6 +275,14 @@ class Book(tree(separator='/'), Workflow, ModelSQL, ModelView):
         context = Transaction().context
 
         query_date = context.get('date', IrDate.today())
+
+        # deny invalid date in context
+        if isinstance(query_date, str):
+            try :
+                dt1 = date.fromisoformat(query_date)
+            except :
+                query_date = IrDate.today()
+
         query = tab_book.join(tab_line,
                 condition=tab_book.id==tab_line.cashbook,
             ).select(
@@ -336,49 +345,62 @@ class Book(tree(separator='/'), Workflow, ModelSQL, ModelView):
         Book2 = pool.get('cashbook.book')
         Currency = pool.get('currency.currency')
         Company = pool.get('company.company')
+        IrDate = pool.get('ir.date')
         tab_book = Book2.__table__()
         tab_comp = Company.__table__()
-        (tab_line, tab2) = cls.get_balance_of_cashbook_sql()
         cursor = Transaction().connection.cursor()
+        context = Transaction().context
 
         result = {x:{y.id: Decimal('0.0') for y in cashbooks} for x in names}
 
+        # deny invalid date in context
+        query_date = context.get('date', IrDate.today())
+        if isinstance(query_date, str):
+            try :
+                dt1 = date.fromisoformat(query_date)
+            except :
+                query_date = IrDate.today()
+
         # query balances of cashbooks and sub-cashbooks
-        tab_subids = sub_ids_hierarchical('cashbook.book')
-        query = tab_book.join(tab_subids,
-                condition=tab_book.id==tab_subids.parent,
-            ).join(tab_comp,
-                condition=tab_book.company==tab_comp.id,
-            ).join(tab_line,
-                condition=tab_line.cashbook==AnyInArray(tab_subids.subids),
-            ).select(
-                tab_book.id,
-                tab_book.currency.as_('to_currency'),
-                tab_line.currency.as_('from_currency'),
-                tab_comp.currency.as_('company_currency'),
-                Sum(tab_line.balance).as_('balance'),
-                Sum(tab_line.balance_all).as_('balance_all'),
-                group_by=[tab_book.id, tab_line.currency, tab_comp.currency],
-                where=tab_book.id.in_([x.id for x in cashbooks]),
-            )
-        cursor.execute(*query)
-        records = cursor.fetchall()
+        with Transaction().set_context({
+            'date': query_date,
+            }):
+            (tab_line, tab2) = cls.get_balance_of_cashbook_sql()
+            tab_subids = sub_ids_hierarchical('cashbook.book')
+            query = tab_book.join(tab_subids,
+                    condition=tab_book.id==tab_subids.parent,
+                ).join(tab_comp,
+                    condition=tab_book.company==tab_comp.id,
+                ).join(tab_line,
+                    condition=tab_line.cashbook==AnyInArray(tab_subids.subids),
+                ).select(
+                    tab_book.id,
+                    tab_book.currency.as_('to_currency'),
+                    tab_line.currency.as_('from_currency'),
+                    tab_comp.currency.as_('company_currency'),
+                    Sum(tab_line.balance).as_('balance'),
+                    Sum(tab_line.balance_all).as_('balance_all'),
+                    group_by=[tab_book.id, tab_line.currency, tab_comp.currency],
+                    where=tab_book.id.in_([x.id for x in cashbooks]),
+                )
+            cursor.execute(*query)
+            records = cursor.fetchall()
 
-        for record in records:
-            values = {
-                'balance': Currency.compute(
-                        record[2], record[4], record[1],
-                    ),
-                'balance_all': Currency.compute(
-                        record[2], record[5], record[1],
-                    ),
-                'balance_ref': Currency.compute(
-                        record[2], record[5], record[3],
-                    ),
-                }
+            for record in records:
+                values = {
+                    'balance': Currency.compute(
+                            record[2], record[4], record[1],
+                        ),
+                    'balance_all': Currency.compute(
+                            record[2], record[5], record[1],
+                        ),
+                    'balance_ref': Currency.compute(
+                            record[2], record[5], record[3],
+                        ),
+                    }
 
-            for name in names:
-                result[name][record[0]] += values[name]
+                for name in names:
+                    result[name][record[0]] += values[name]
         return result
 
     @fields.depends('btype')