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You can create aA module with thecan be created using following files:

<?xml version="1.0"?>
<config>
    <sections>
        <custom translate="label" module="module">
            <label>Custom</label>
            <tab>general</tab>
            <sort_order>60</sort_order>
            <show_in_default>1</show_in_default>
            <show_in_website>1</show_in_website>
            <show_in_store>1</show_in_store>
            <groups>                    
                <custom_group>
                    <fields>
                        <hours translate="label">
                            <label>Store Contact Hours</label>
                            <frontend_type>text</frontend_type>
                            <sort_order>21</sort_order>
                            <show_in_default>1</show_in_default>
                            <show_in_website>1</show_in_website>
                            <show_in_store>1</show_in_store>
                        </hours>
                    </fields>
                </custom_group>
            </groups>
        </custom>
    </section>sections>
</config>

In this example, theThe value of the field will be accessible by Mage::getStoreConfig('custom/custom_group/hours');

You can create a module with the following files:

<?xml version="1.0"?>
<config>
    <sections>
        <custom translate="label" module="module">
            <label>Custom</label>
            <tab>general</tab>
            <sort_order>60</sort_order>
            <show_in_default>1</show_in_default>
            <show_in_website>1</show_in_website>
            <show_in_store>1</show_in_store>
            <groups>                    
                <custom_group>
                    <fields>
                        <hours translate="label">
                            <label>Store Contact Hours</label>
                            <frontend_type>text</frontend_type>
                            <sort_order>21</sort_order>
                            <show_in_default>1</show_in_default>
                            <show_in_website>1</show_in_website>
                            <show_in_store>1</show_in_store>
                        </hours>
                    </fields>
                </custom_group>
            </groups>
        </custom>
    </section>
</config>

In this example, the value of the field will be accessible by Mage::getStoreConfig('custom/custom_group/hours');

A module can be created using following files:

<?xml version="1.0"?>
<config>
    <sections>
        <custom translate="label" module="module">
            <label>Custom</label>
            <tab>general</tab>
            <sort_order>60</sort_order>
            <show_in_default>1</show_in_default>
            <show_in_website>1</show_in_website>
            <show_in_store>1</show_in_store>
            <groups>                    
                <custom_group>
                    <fields>
                        <hours translate="label">
                            <label>Store Contact Hours</label>
                            <frontend_type>text</frontend_type>
                            <sort_order>21</sort_order>
                            <show_in_default>1</show_in_default>
                            <show_in_website>1</show_in_website>
                            <show_in_store>1</show_in_store>
                        </hours>
                    </fields>
                </custom_group>
            </groups>
        </custom>
    </sections>
</config>

The value of the field will be accessible by Mage::getStoreConfig('custom/custom_group/hours');

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app/etc/modules/Vendor_Module.xml

<?xml version="1.0"?>
<config>
    <modules>
        <Vendor_Module>
            <active>true</active>
            <codePool>local</codePool>
        </Vendor_Module>
    </modules>
</config>

app/code/local/Vendor/Module/etc/config.xml

<?xml version="1.0"?>
<config>
    <modules>
        <Vendor_Module>
            <version>0.0.1</version>
        </Vendor_Module>
    </modules>
    <global>
        <helpers>
            <class>Vendor_Module_Helper</class>
        </helpers>
    </global>
</config>
<?xml version="1.0"?>
<config>
    <sections>
        <general><custom translate="label" module="module">
            <label>Custom</label>
            <tab>general</tab>
            <sort_order>60</sort_order>
            <show_in_default>1</show_in_default>
            <show_in_website>1</show_in_website>
            <show_in_store>1</show_in_store>
            <groups>                    
                <store_information><custom_group>
                    <fields>
                        <hours translate="label">
                            <label>Store Contact Hours</label>
                            <frontend_type>text</frontend_type>
                            <sort_order>21</sort_order>
                            <show_in_default>1</show_in_default>
                            <show_in_website>1</show_in_website>
                            <show_in_store>1</show_in_store>
                        </hours>
                    </fields>
                </store_information>custom_group>
            </groups>
        </general>custom>
    </section>
</config>

app/code/local/Vendor/Module/Helper/Data.php

<?php

class Vendor_Module_Helper_Data extends Mage_Core_Helper_Abstract
{
}

In this example, the value of the field will be accessible by Mage::getStoreConfig('general'custom/store_informationcustom_group/hours');

app/code/local/Vendor/Module/etc/config.xml

<?xml version="1.0"?>
<config>
    <modules>
        <Vendor_Module>
            <version>0.0.1</version>
        </Vendor_Module>
    </modules>
</config>
<?xml version="1.0"?>
<config>
    <sections>
        <general>
            <groups>
                <store_information>
                    <fields>
                        <hours translate="label">
                            <label>Store Contact Hours</label>
                            <frontend_type>text</frontend_type>
                            <sort_order>21</sort_order>
                            <show_in_default>1</show_in_default>
                            <show_in_website>1</show_in_website>
                            <show_in_store>1</show_in_store>
                        </hours>
                    </fields>
                </store_information>
            </groups>
        </general>
    </section>
</config>

In this example, the value of the field will be accessible by Mage::getStoreConfig('general/store_information/hours');

app/etc/modules/Vendor_Module.xml

<?xml version="1.0"?>
<config>
    <modules>
        <Vendor_Module>
            <active>true</active>
            <codePool>local</codePool>
        </Vendor_Module>
    </modules>
</config>

app/code/local/Vendor/Module/etc/config.xml

<?xml version="1.0"?>
<config>
    <modules>
        <Vendor_Module>
            <version>0.0.1</version>
        </Vendor_Module>
    </modules>
    <global>
        <helpers>
            <class>Vendor_Module_Helper</class>
        </helpers>
    </global>
</config>
<?xml version="1.0"?>
<config>
    <sections>
        <custom translate="label" module="module">
            <label>Custom</label>
            <tab>general</tab>
            <sort_order>60</sort_order>
            <show_in_default>1</show_in_default>
            <show_in_website>1</show_in_website>
            <show_in_store>1</show_in_store>
            <groups>                    
                <custom_group>
                    <fields>
                        <hours translate="label">
                            <label>Store Contact Hours</label>
                            <frontend_type>text</frontend_type>
                            <sort_order>21</sort_order>
                            <show_in_default>1</show_in_default>
                            <show_in_website>1</show_in_website>
                            <show_in_store>1</show_in_store>
                        </hours>
                    </fields>
                </custom_group>
            </groups>
        </custom>
    </section>
</config>

app/code/local/Vendor/Module/Helper/Data.php

<?php

class Vendor_Module_Helper_Data extends Mage_Core_Helper_Abstract
{
}

In this example, the value of the field will be accessible by Mage::getStoreConfig('custom/custom_group/hours');

1
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You can create a module with the following files:

app/code/local/Vendor/Module/etc/config.xml

<?xml version="1.0"?>
<config>
    <modules>
        <Vendor_Module>
            <version>0.0.1</version>
        </Vendor_Module>
    </modules>
</config>

app/code/local/Vendor/Module/etc/system.xml

<?xml version="1.0"?>
<config>
    <sections>
        <general>
            <groups>
                <store_information>
                    <fields>
                        <hours translate="label">
                            <label>Store Contact Hours</label>
                            <frontend_type>text</frontend_type>
                            <sort_order>21</sort_order>
                            <show_in_default>1</show_in_default>
                            <show_in_website>1</show_in_website>
                            <show_in_store>1</show_in_store>
                        </hours>
                    </fields>
                </store_information>
            </groups>
        </general>
    </section>
</config>

In this example, I've added a Store Contact Hours field but you can change it to whatever you want.

In this example, the value of the field will be accessible by Mage::getStoreConfig('general/store_information/hours');