Fixed DataFrame widget datetime formatting (#1221)

* Fixed DataFrame widget datetime formatting

* Add test

panel/tests/widgets/test_tables.py

@@ -4,12 +4,13 @@
 
 try:
     import pandas as pd
+    from pandas.util.testing import makeTimeDataFrame
 except ImportError:
     pytestmark = pytest.mark.skip('pandas not available')
 
 from bokeh.models.widgets.tables import (
     NumberFormatter, IntEditor, NumberEditor, StringFormatter,
-    SelectEditor
+    SelectEditor, DateFormatter, DateEditor
 )
 
 from panel.widgets import DataFrame
@@ -40,6 +41,19 @@ def test_dataframe_widget(dataframe, document, comm):
     assert isinstance(float_col.editor, NumberEditor)
 
 
+def test_dataframe_widget_datetimes(document, comm):
+
+    table = DataFrame(makeTimeDataFrame())
+
+    model = table.get_root(document, comm)
+
+    dt_col, _, _, _, _ = model.columns
+
+    assert dt_col.title == 'index'
+    assert isinstance(dt_col.formatter, DateFormatter)
+    assert isinstance(dt_col.editor, DateEditor)
+
+
 def test_dataframe_editors(dataframe, document, comm):
     editor = SelectEditor(options=['A', 'B', 'C'])
     table = DataFrame(dataframe, editors={'str': editor})

panel/widgets/tables.py

@@ -68,12 +68,13 @@ def _get_columns(self):
             elif kind == 'f':
                 formatter = NumberFormatter(format='0,0.0[00000]')
                 editor = NumberEditor()
-            elif isdatetime(data):
+            elif isdatetime(data) or kind == 'M':
                 formatter = DateFormatter(format='%Y-%m-%d %H:%M:%S')
                 editor = DateEditor()
             else:
                 formatter = StringFormatter()
                 editor = StringEditor()
+
             if col in self.editors:
                 editor = self.editors[col]
             if col in self.formatters: