Gravity Forms date field validation filters by cutoff date.

gforms-field-validation-date.php

<?php // Gravity Forms date field validation 
add_filter( 'gform_field_validation_2_10', 'shopguide_gform_validation_2_10', 10, 4 );
function shopguide_gform_validation_2_10( $result, $value, $form, $field ) 
{
    $valid           = false;
    $day_select      = date( 'D', $value ); 
    $date_selected   = strtotime( $value );
    $now             = strtotime( 'now' );
    $wed_next        = strtotime( 'next Wednesday' ); 
    $this_fri        = strtotime( 'next Friday');
        if( $now < $this_fri ) 
        {
            $wed_to_use = strtotime('+7 days', $wed_next );
        } else 
            {
            $wed_to_use = strtotime('+14 days', $wed_next );
        }
    
        // false on !wed
        if ( intval($date_selected) < $wed_to_use - 388800 ) 
            {
                $valid = false;
            } 
                /* otherwise true */
                else 
                {
                    $valid = true;
                }

    if ( !$valid ) { 
        $result["is_valid"] = false; 
        $result["message"] = '<div class="validation_error">' . esc_html__( 'You missed the cutoff time for ads. 
        Please select a Wednesday on or after ', 'gravityforms' ) . ' ' . date('m/d/Y', $wed_to_use) . '</div>';
       
    } else {
        $result["is_valid"] = true; 
    }   
        return $result;
}
/**
 * $result, $value, $form, $field
 * @param string $value         Value of date selection
 * @param string $now           Time now
 * @param string $day_select    Day option
 * @param string $date_selected Day option
 * @param string $cutoff        5PM
 * 
 * @return Boolean              Process success or error message
 * @see https://docs.gravityforms.com/using-gform-validation-hook/
 * 
 */