Date / time validation?

Thank you for your reply, Carlos.

I managed to find a custom validation article on contact form 7 and it teaches me to code the following to check if end date is earlier than the start date. Just posting here in case in future others may need it:

// to check if form end date is earlier than start date
add_filter( 'wpcf7_validate_text', 'custom_email_confirmation_validation_filter', 20, 2 );
 
function custom_email_confirmation_validation_filter( $result, $tag ) {
    if ( 'enddate' == $tag->name ) {
               
        $dateTimestamp1 = strtotime($_POST['startdate']); 
        $dateTimestamp2 = strtotime($_POST['enddate']); 
        
        if ( $dateTimestamp1 > $dateTimestamp2) {
            $result->invalidate( $tag, "End date cannot be earlier than Start date!" );
        }
    }
 
    return $result;
}

The article for reference is at – https://contactform7.com/2015/03/28/custom-validation/