Magento layout xml files can be really confusing. Here is a post to make them even more confusing, but really useful.
I won’t cover how to create a layout xml file here, I’ll cover that in a different post. I’m going to show you how to re-use the handles in your module.
Let’s say your module has the following layout xml. It’s just a one page module so it is simple:

<?xml version="1.0"?>
<layout version="1.0.0">
    <mymodule_default>
        <reference name="head">
            <action method="addItem">
                <type>skin_css</type>
                <name>css/mymodule.css</name>
            </action>
            <action method="addItem">
                <type>skin_js</type>
                <name>src/js/mymodule.js</name>
            </action>
        </reference>
    </mymodule_default>
    <mymodule_index_index>
        <update handle="mymodule_default" />
        <reference name="content">
            <block type="core/template" name="mymodule.main" template="mymodule/index.phtml">
                <block type="core/template" name="mymodule.child1" template="mymodule/index/childblock1.phtml"/>
                <block type="core/template" name="mymodule.child2" template="mymodule/index/childblock2.phtml"/>
            </block>
        </reference>
    </q_index_index>
</layout>

Take a look at the <update handle="mymodule_default" /> line in the <mymodule_index_index> section.What that is doing is copying everything in the <mymodule_default> section into that section.
This is really useful. You can use this same method to copy basically any block into another block.
For example, lets say you want to create a new section that includes the same templates that are in your <mymodule_index_index> section. You would add this to your xml:

<mymodule_newblock_index>
    <update handle="mymodule_index_index" />
</mymodule_newblock_index>

That section would include everything that is in the <mymodule_index_index> section.
Have fun re-using handles!

class My_Custom_Block extends Mage_Catalog_Block_Product_View_Abstract {

    protected function _construct()
    {
        // the $groupId make it so each customer group will be cached separately
        $groupId = Mage::getSingleton('customer/session')->getCustomerGroupId();
        $this->addData(array(
            'cache_lifetime' => 5600,
            'cache_tags' => array(Mage_Core_Model_Store::CACHE_TAG, Mage_Cms_Model_Block::CACHE_TAG),
            // you can add anything to the cache_key to make it cache separate versions for different customers and stores
            'cache_key' => "custom_unique_name_{$groupId}"
        ));
    }
}

You can create an XML sitemap for you Magento store by logging into your administration panel and going to Catalog > Google Sitemap.

This interface is pretty straightforward, just be aware that each store must have its own sitemap. Also note that the the Path must be writable by the file system.

When you click “Save & Generate” a new xml sitemap will be generated. The frequency and priority are set using default settings but can be changed in System > Configuration > Catalog: Google Sitemap. This is also where you will set up your sitemaps to be automatically generated by the Magento cron job.

The Magento sitemap only includes catalog categories, products, and CMS pages by default. Lets discuss how to customize what is included in the sitemaps.

Customizing Magento’s XML Sitemap

The generateXml() function in the Mage_Sitemap_Model_Sitemap class is where all of the magic happens. We are going to overwrite this function. I’m not going to get into extending and overwriting Magento core here, if you need to learn about it you can read my post about it.

The generateXml() function has a lot going on, so to make it easier I just copy the entire function into my new class and never refer to the original function.

I recommend putting your custom code near the end of the function just after the last unset($collection); in the “Generate cms pages sitemap” section. I also recommend copying the same structure that the other sections use.

Here is what my custom code looks like with comments:

/**
 * Generate customurls sitemap
 */
// reuse same settings as the cms page section, you can create custom ones if you know how
$changefreq = (string)Mage::getStoreConfig('sitemap/page/changefreq', $storeId);
$priority   = (string)Mage::getStoreConfig('sitemap/page/priority', $storeId);

// you can do a lot of things to get these urls, this is a simplified example
$collection = array(
    'module1/page1',
    'module1/page2',
    'module2/page1'
);

// this is the most important part, it writes the data to the xml file
foreach ($collection as $item) {
    $xml = sprintf(
        '%s%s%s%.1f',
        // the core function concatenates $baseUrl with the url,
        // you can also use ->getUrl() or some other method to get the url
        htmlspecialchars($baseUrl . $item),
        $date,
        $changefreq,
        $priority
    );
    $io->streamWrite($xml);
}
unset($collection);

This is a very basic example. There are many ways to customize this, but this will get you started.

Go back to Catalog > Google Sitemap and click “Save & Generate” and then go to your sitemap url to see if the new urls are there.

The days of using crontab to run cron jobs for your Magento installation are long over. Since Magento Community Edition 1.8 (Enterprise Edition 1.13) cron jobs can now be configured using the Magento configuration.

Initial Setup

Before you can schedule your cron jobs, you have to set up Magento’s cron.php or cron.sh using crontab. This will be the only time you will ever have to use crontab.
Using cron.php:

* * * * * /bin/php /var/www/magento/cron.php

Using cron.sh:

* * * * * /bin/sh /var/www/magento/cron.sh

These examples are setup to continuously check for scheduled cron jobs. You can change how often Magento checks for scheduled cron jobs, just make sure you know what you are doing first.

Scheduling a Cron Job

Now that the Magento cron job is setup, you can start scheduling custom cron jobs. You do this by adding a crontab block to the end of the config.xml file of your module:

<config>
...
...
    <crontab>
        <jobs>
            <my_cron_job>
                <schedule>
                    <cron_expr>0 1 * * *</cron_expr>
                </schedule>
                <run>
                    <model>mymodule/observer::myFunctionName</model>
                </run>
            </my_cron_job>
        </jobs>
    </crontab>
<config>

This particular example will run the myFunctionName() function in the observer.php of the “mymodule” module every morning at 1:00am.

That’s it!

There are a few things to be aware of when saving dates in Magento. Magento comes built in with a lot of tools that allow you to work with dates, learning to use these tools will help you improve the consistency and quality of your Magento code as well as increasing your Magento skills. In this post we will only focus on saving dates in the database and then displaying them in a template.

Saving datetime in database

We are going to assume that you already know how to create a new model and database table for the model. Core Magento is programmed to save all datetimes in the database in GMT time, so that is what we are going to do. Here is an easy way to do that correctly:

First, you need to make sure all of the dates are converted to Magento’s internal format as specified in

Varien_Date::DATETIME_INTERNAL_FORMAT

An easy way to do that is to use the

_filterDateTime()

function in the

Mage_Core_Controller_Varien_Action

class (the class should already be inherited by your controller so you can use “$this”). Here is an example using dates submitted by a form:

$params = $this->getRequest()->getParams();

$params = $this->_filterDateTime($params, array('date','date2','date3'));

Once you have formated the datetime, you will need to convert it to GMT like this:

$date = Mage::getModel('core/date')->gmtDate('Y-m-d H:i:s',$params['date'])

Now that it is properly converted to GMT you can save it in your model:

$model->setDate($date)->save()

Showing datetime in template

Here is how you would use Magento’s built in tools to display a datetime that is saved in GMT:

$this->formatDate($date, Mage_Core_Model_Locale::FORMAT_TYPE_SHORT, true)

The formatDate() function will automatically convert the datetime to whichever timezone the user is in. The code above will output the date followed by the time like this:

01/19/2016 10:42 am

If you don’t need to show the time, then just remove the “true” parameter from the formatDate() function.

There you go! Enjoy Magento’s datetime tools!