Permit customization of date display. The format string can be anything accepted by QDate, with a default of dd MMM yyyy (set in library.py):

d	the day as number without a leading zero (1 to 31)
dd	the day as number with a leading zero (01 to 31)
ddd	the abbreviated localized day name (e.g. 'Mon' to 'Sun').
dddd	the long localized day name (e.g. 'Monday' to 'Sunday'). 
M	the month as number without a leading zero (1 to 12)
MM	the month as number with a leading zero (01 to 12)
MMM	the abbreviated localized month name (e.g. 'Jan' to 'Dec').
MMMM	the long localized month name (e.g. 'January' to 'December').
yy	the year as two digit number (00 to 99)
yyyy	the year as four digit number. If the year is negative, a minus sign is prepended in addition.

src/calibre/gui2/dialogs/config/__init__.py

@@ -776,14 +776,17 @@ class ConfigDialog(ResizableDialog, Ui_Dialog):
                                 label=c,
                                 name=self.custcols[c]['name'],
                                 datatype=self.custcols[c]['datatype'],
-                                is_multiple=self.custcols[c]['is_multiple'])
+                                is_multiple=self.custcols[c]['is_multiple'],
+                                display = self.custcols[c]['display'])
                 must_restart = True
             elif '*deleteme' in self.custcols[c]:
                 self.db.delete_custom_column(label=c)
                 must_restart = True
             elif '*edited' in self.custcols[c]:
                 cc = self.custcols[c]
-                self.db.set_custom_column_metadata(cc['num'], name=cc['name'], label=cc['label'])
+                self.db.set_custom_column_metadata(cc['num'], name=cc['name'],
+                                                   label=cc['label'],
+                                                   display = self.custcols[c]['display'])
                 if '*must_restart' in self.custcols[c]:
                     must_restart = True
 

src/calibre/gui2/dialogs/config/create_custom_column.py

@@ -48,9 +48,9 @@ class CreateCustomColumn(QDialog, Ui_QCreateCustomColumn):
         self.editing_col = editing
         self.standard_colheads = standard_colheads
         self.standard_colnames = standard_colnames
-        if not self.editing_col:
         for t in self.column_types:
             self.column_type_box.addItem(self.column_types[t]['text'])
+        if not self.editing_col:
             self.exec_()
             return
         idx = parent.columns.currentRow()
@@ -68,7 +68,10 @@ class CreateCustomColumn(QDialog, Ui_QCreateCustomColumn):
         self.orig_column_number = c['num']
         self.orig_column_name = col
         column_numbers = dict(map(lambda x:(self.column_types[x]['datatype'], x), self.column_types))
-        self.column_type_box.addItem(self.column_types[column_numbers[ct]]['text'])
+        self.column_type_box.setCurrentIndex(column_numbers[ct])
+        self.column_type_box.setEnabled(False)
+        if ct == 'datetime':
+            self.date_format_box.setText(c['display'].get('date_format', ''))
         self.exec_()
 
     def accept(self):
@@ -105,13 +108,18 @@ class CreateCustomColumn(QDialog, Ui_QCreateCustomColumn):
         if ':' in col or ' ' in col or col.lower() != col:
             return self.simple_error('', _('The lookup name must be lower case and cannot contain ":"s or spaces'))
 
+        date_format = None
+        if col_type == 'datetime':
+            if self.date_format_box.text():
+                date_format = {'date_format':unicode(self.date_format_box.text())}
+
         if not self.editing_col:
             self.parent.custcols[col] = {
                     'label':col,
                     'name':col_heading,
                     'datatype':col_type,
                     'editable':True,
-                    'display':None,
+                    'display':date_format,
                     'normalized':None,
                     'num':None,
                     'is_multiple':is_multiple,
@@ -127,6 +135,7 @@ class CreateCustomColumn(QDialog, Ui_QCreateCustomColumn):
             item.setText(col_heading)
             self.parent.custcols[self.orig_column_name]['label'] = col
             self.parent.custcols[self.orig_column_name]['name'] = col_heading
+            self.parent.custcols[self.orig_column_name]['display'] = date_format
             self.parent.custcols[self.orig_column_name]['*edited'] = True
             self.parent.custcols[self.orig_column_name]['*must_restart'] = True
         QDialog.accept(self)

src/calibre/gui2/dialogs/config/create_custom_column.ui

@@ -10,7 +10,7 @@
     <x>0</x>
     <y>0</y>
     <width>528</width>
-    <height>165</height>
+    <height>194</height>
    </rect>
   </property>
   <property name="sizePolicy">
@@ -33,6 +33,9 @@
      </property>
      <item row="2" column="0">
       <layout class="QGridLayout" name="gridLayout">
+       <property name="margin">
+        <number>0</number>
+       </property>
        <item row="0" column="0">
         <widget class="QLabel" name="label_2">
          <property name="text">
@@ -102,6 +105,43 @@
          </property>
         </widget>
        </item>
+       <item row="4" column="1">
+        <layout class="QHBoxLayout" name="horizontalLayout_3">
+         <item>
+          <widget class="QLineEdit" name="date_format_box">
+           <property name="sizePolicy">
+            <sizepolicy hsizetype="Maximum" vsizetype="Fixed">
+             <horstretch>0</horstretch>
+             <verstretch>0</verstretch>
+            </sizepolicy>
+           </property>
+           <property name="toolTip">
+            <string>Date format. Use 1-4 'd's for day, 1-4 'M's for month, and 1-2 'Y's for year.</string>
+           </property>
+          </widget>
+         </item>
+         <item>
+          <widget class="QLabel" name="label_5">
+           <property name="toolTip">
+            <string>Use MMM yyyy for month + year, yyyy for year only</string>
+           </property>
+           <property name="text">
+            <string>Default: dd MMM yyyy.</string>
+           </property>
+          </widget>
+         </item>
+        </layout>
+       </item>
+       <item row="4" column="0">
+        <widget class="QLabel" name="label_4">
+         <property name="text">
+          <string>Format for dates</string>
+         </property>
+         <property name="buddy">
+          <cstring>date_format_box</cstring>
+         </property>
+        </widget>
+       </item>
       </layout>
      </item>
      <item row="3" column="0">
@@ -138,6 +178,7 @@
   <tabstop>column_name_box</tabstop>
   <tabstop>column_heading_box</tabstop>
   <tabstop>column_type_box</tabstop>
+  <tabstop>date_format_box</tabstop>
   <tabstop>button_box</tabstop>
  </tabstops>
  <resources/>

src/calibre/gui2/library.py

@@ -177,6 +177,33 @@ class TagsDelegate(QStyledItemDelegate):
             editor = EnLineEdit(parent)
         return editor
 
+class CcDateDelegate(QStyledItemDelegate):
+    '''
+    Delegate for custom columns dates. Because this delegate stores the
+    format as an instance variable, a new instance must be created for each
+    column. This differs from all the other delegates.
+    '''
+
+    def set_format(self, format):
+        if not format:
+            self.format = 'dd MMM yyyy'
+        else:
+            self.format = format
+
+    def displayText(self, val, locale):
+        d = val.toDate()
+        if d == UNDEFINED_DATE:
+            return ''
+        return d.toString(self.format)
+
+    def createEditor(self, parent, option, index):
+        qde = QStyledItemDelegate.createEditor(self, parent, option, index)
+        qde.setDisplayFormat(self.format)
+        qde.setMinimumDate(UNDEFINED_DATE)
+        qde.setSpecialValueText(_('Undefined'))
+        qde.setCalendarPopup(True)
+        return qde
+
 class CcTextDelegate(QStyledItemDelegate):
     '''
     Delegate for text/int/float data.
@@ -989,7 +1016,9 @@ class BooksView(TableView):
                 continue
             cc = self._model.custom_columns[colhead]
             if cc['datatype'] == 'datetime':
-                self.setItemDelegateForColumn(cm.index(colhead), self.timestamp_delegate)
+                delegate = CcDateDelegate(self)
+                delegate.set_format(cc['display'].get('date_format',''))
+                self.setItemDelegateForColumn(cm.index(colhead), delegate)
             elif cc['datatype'] == 'comments':
                 self.setItemDelegateForColumn(cm.index(colhead), self.cc_comments_delegate)
             elif cc['datatype'] == 'text':