How to set a date field in a ui form to be mandatory?

normal Date field in the form

       <field name="date_of_birth" formElement="date">
            <argument name="data" xsi:type="array">
                <item name="config" xsi:type="array">
                    <item name="source" xsi:type="string">Date of birth</item>
                </item>     
                <item name="validation" xsi:type="array">
                    <!-- <item name="required-entry" xsi:type="boolean">true</item>
                    <item name="validate-date" xsi:type="boolean">true</item> -->
                    <item name="date-required-custom" xsi:type="boolean">true</item>
                </item>    
            </argument>
            <settings>
                <dataType>timestamp</dataType>
                <label translate="true">Date of birth</label>
                <visible>true</visible>
                <dataScope>date_of_birth</dataScope>
            </settings>
        </field> 

need to modify with required fields with the new required field

<field name="date_of_birth">
    <argument name="data" xsi:type="array">
        <item name="config" xsi:type="array">
            <item name="dataType" xsi:type="string">string</item>
            <item name="label" xsi:type="string" translate="true">Date of birth</item>
            <item name="formElement" xsi:type="string">date</item>
            <item name="source" xsi:type="string">page</item>
            <item name="sortOrder" xsi:type="number">21</item>
            <item name="dataScope" xsi:type="string">date_of_birth</item>
            <item name="validation" xsi:type="array">
                <item name="required-entry" xsi:type="boolean">true</item>
            </item>
            <item name="options" xsi:type="array">
                <item name="dateFormat" xsi:type="string">yyyy-MM-dd</item>
                <item name="timeFormat" xsi:type="string">HH:mm:ss</item>
                <item name="showsTime" xsi:type="boolean">true</item>
            </item>
            <item name="storeTimeZone" xsi:type="string">string</item>
        </item>
    </argument>
</field>