All previous answers were incomplete. Here are the complete steps.
Create the following file at app/code/local/YourCompany/YourModule/etc/config.xml:
<?xml version="1.0"?>
<config>
<modules>
<YourCompany_YourModule>
<version>0.0.1</version>
</YourCompany_YourModule>
</modules>
<global>
<blocks>
<currentdate>
<class>YourCompany_YourModule_Block</class>
</currentdate>
</blocks>
</global>
</config>
Create the following file at app/code/local/YourCompany/YourModule/Block/Datetoday.php
<?php
class YourCompany_YourModule_Block_Datetoday extends Mage_Core_Block_Text
{
protected function _toHtml()
{
$date = Mage::getModel('core/date')->date('m-d-Y H:i:s');
$this->setText($date);
return $this->getText();
}
}
Create this file at app/etc/modules/YourCompany_YourModule.xml
<?xml version="1.0"?>
<config>
<modules>
<YourCompany_YourModule>
<active>true</active>
<codePool>local</codePool>
</YourCompany_YourModule>
</modules>
</config>
Add a permission for the block YourModule/datetoday
in the admin panel.
Perform a cache refresh.