Hello Magento friends here we are create a Admin Configuration form in magento2 :
<?xml version="1.0"?>
<config
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Config:etc/system_file.xsd">
<system>
<section id="carriers" showInDefault="1" showInStore="1" showInWebsite="1" sortOrder="1000" translate="label">
<group id="deliverydateandtime" showInDefault="1" showInStore="1" showInWebsite="1" sortOrder="10" translate="label">
<label>Pickup Date Shipping Method Group</label>
<field id="active" showInDefault="1" showInStore="1" showInWebsite="1" sortOrder="10" translate="label" type="select" canRestore="1">
<label>Enabled</label>
<source_model>Magento\Config\Model\Config\Source\Yesno</source_model>
</field>
<field id="name" showInDefault="1" showInStore="1" showInWebsite="1" sortOrder="20" translate="label" type="text" canRestore="1">
<label>Method Name</label>
</field>
<field id="price" showInDefault="1" showInStore="1" showInWebsite="1" sortOrder="30" translate="label" type="text" canRestore="1">
<label>Price</label>
<validate>validate-number</validate>
</field>
<field id="sort_order" showInDefault="1" showInStore="1" showInWebsite="1" sortOrder="51" translate="label" type="text">
<label>Sort Order</label>
</field>
<field id="title" showInDefault="1" showInStore="1" showInWebsite="1" sortOrder="50" translate="label" type="text" canRestore="1">
<label>Title</label>
</field>
<field id="format" translate="label" type="text" sortOrder="10" showInDefault="1" showInWebsite="1" showInStore="1" canRestore="1">
<label>Date Format:</label>
<comment>yy-mm-dd</comment>
</field>
<field id="startdate" translate="label" type="text" sortOrder="11" showInDefault="1" showInWebsite="1" canRestore="1" showInStore="1">
<label>Start Date of the Slot</label>
<comment>today-today, tommarow:+1d, next day to strat :+1d,+2d,+3d,+4d</comment>
</field>
<field id="starttimne" translate="label" sortOrder="12" type="time" showInDefault="1" showInWebsite="1" showInStore="1">
<label>Start Time of the Slot</label>
</field>
<field id="enddate" translate="label" type="text" sortOrder="13" showInDefault="1" showInWebsite="1" canRestore="1" showInStore="1">
<label>End Date of the Slot</label>
<comment>today-today, tommarow:+1d, next day to strat :+1d,+2d,+3d,+4d</comment>
</field>
<field id="optiondeliverytime" translate="label" type="multiselect" sortOrder="14" showInDefault="1" showInWebsite="1" showInStore="1">
<label>Delivery Time Options </label>
<source_model>SR\DeliveryDate\Model\Adminhtml\System\Config\Source\DeliveryTime</source_model>
<can_be_empty>1</can_be_empty>
</field>
<field id="cutofminute" translate="label" type="text" sortOrder="15" showInDefault="1" showInWebsite="1" showInStore="1" canRestore="1">
<label>Cut of Time:</label>
<comment>in minute</comment>
</field>
</group>
</section>
</system>
</config>
this is file is default config.xml it is used to set deault value of above form
<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Store:etc/config.xsd">
<default>
<carriers>
<deliverydateandtime>
<format>yy-mm-dd</format>
<disabled>-1</disabled>
<hourMin>8</hourMin>
<hourMax>22</hourMax>
<active>1</active>
<startdate>+1d</startdate>
<enddate>+7d</enddate>
<cutofminute>59</cutofminute>
<sallowspecific>0</sallowspecific>
<model>SR\DeliveryDate\Model\Carrier\Shipping</model>
<name>Pickup Rate</name>
<title>Pickup Date and Time</title>
<price>10</price>
<specificerrmsg>This shipping method is not available. To use this shipping method, please contact us.</specificerrmsg>
<handling_type>F</handling_type>
</deliverydateandtime>
</carriers>
</default>
</config>