diff --git a/src/calibre/db/cache.py b/src/calibre/db/cache.py
index 3b5c29574a..e5aaa4d642 100644
--- a/src/calibre/db/cache.py
+++ b/src/calibre/db/cache.py
@@ -102,8 +102,9 @@ def _add_default_custom_column_values(mi, fm):
                     mi.set_user_metadata(cc, col)
                 dt = col['datatype']
                 if dt == 'bool':
-                    dv = {_('yes'): 'true', _('no'): 'false'}.get(icu_lower(dv), '')
-                elif dt == 'datetime' and icu_lower(dv) == _('now'):
+                    dv = {_('yes'): 'true', 'yes': 'true',
+                          _('no'): 'false', 'no': 'false'}.get(icu_lower(dv), '')
+                elif dt == 'datetime' and (icu_lower(dv) in [_('now'), 'now']):
                     dv = nowf()
                 elif dt == 'rating':
                     try:
@@ -112,7 +113,7 @@ def _add_default_custom_column_values(mi, fm):
                         dv = None
                 mi.set(cc, dv)
         except:
-            pass
+            traceback.print_exc()
 
 
 dynamic_category_preferences = frozenset({'grouped_search_make_user_categories', 'grouped_search_terms', 'user_categories'})
diff --git a/src/calibre/gui2/preferences/create_custom_column.py b/src/calibre/gui2/preferences/create_custom_column.py
index 9f2b5f0a77..9139875ff7 100644
--- a/src/calibre/gui2/preferences/create_custom_column.py
+++ b/src/calibre/gui2/preferences/create_custom_column.py
@@ -396,11 +396,12 @@ class CreateCustomColumn(QDialog):
 
         # Default value
         self.default_value = dv = QLineEdit(self)
-        dv.setToolTip('<p>' + _('Default value when a new book is added to the '
-            'library. For Date columns enter the word "now" or the date as '
-            'yyyy-mm-dd. For Yes/No columns enter "Yes" or "No". For Text with '
-            'a fixed set of values enter one of the permitted values. For '
-            'Rating columns enter a number between 0 and 5.') + '</p>')
+        dv.setToolTip('<p>' + (_('Default value when a new book is added to the '
+            'library. For Date columns enter the word "Now" or "%s", or the '
+            'date as yyyy-mm-dd. For Yes/No columns enter "Yes" or "%s", or '
+            '"No" or "%s". For Text with a fixed set of values enter one of '
+            'the permitted values. For Rating columns enter a number between '
+            '0 and 5.') % ('now', 'yes', 'no')) + '</p>')
         self.default_value_label = add_row(_('Default value'), dv)
 
         self.resize(self.sizeHint())