Resolve "exceeded visits list & unfinished visits list"

Closes #146 (closed)

smash/web/api_views/serialization_utils.py

@@ -24,6 +24,22 @@ def location_to_str(location):
     return result
 
 
+def serialize_date(date):
+    if date is not None:
+        result = date.strftime('%Y-%m-%d')
+    else:
+        result = ""
+    return result
+
+
+def serialize_datetime(date):
+    if date is not None:
+        result = date.strftime('%Y-%m-%d %H:%M')
+    else:
+        result = ""
+    return result
+
+
 def add_column(result, name, field_name, column_list, param, columns_used_in_study=None, visible_param=None,
                sortable=True):
     add = True