How to add a datetime picker input field in admin module form in magento 1.x

To add a date/time input field in admin form in magento 1.x, you need to simply use code like below:

$dateFormatIso = Mage::app()->getLocale()->getDateTimeFormat(Mage_Core_Model_Locale::FORMAT_TYPE_SHORT);

$fieldset->addField(‘time_from’, ‘date’, array(
‘name’ => ‘time_from’,
‘class’ => ‘required-entry’,
‘required’ => true,
‘label’ => Mage::helper(‘event’)->__(‘Time From’),
‘image’ => $this->getSkinUrl(‘images/grid-cal.gif’),
‘input_format’ => Varien_Date::DATETIME_INTERNAL_FORMAT,
‘format’ => $dateFormatIso,
‘time’ => true, //if you don’t want time, then simply set ‘time’ => false,
));