I cannot reproduce this. After fixing bug #14130 the monthdayyear 
attribute is displayed both in the summary and the history.

This ticket is related to ticket #14130.

After fixing the monthdayyear object so that it would be usable in 
whups I noticed that its history does not get displayed properly, the 
amended value never showed up.

In pear module Form the class of the monthdayyear object is defined in 
file Form/Type.php. Its init() method is defined in line 2851:
class Horde_Form_Type_monthdayyear extends Horde_Form_Type 
{$start_year = '', $end_year = '', $picker = true,
                    $format_in = null, $format_out = '%x')

The init() method accepts 5 arguments, the last of which is 
$format_out and has a default value of '%x'. In line 2865 the 
protected variable $this->_format_out is unconditionally set to 
$format_out. However, at least in the context of a user defined 
attribute in whups, the init() method is called with $format_out = 
null, which causes incorrect rendering of the variable saved in the 
history (i.e. no rendering at all).

I fixed this by checking that $format_out is not null before 
overwriting the protected variable:

         if ($format_out != null) { // line 2865: don't overwrite the 
default value with null
           $this->_format_out = $format_out;