prefix_date_field_params_after_time.php

<?php
/**
 * Set the minimum date differently if we're currently later than 14:00
 */
function prefix_date_field_params_after_time( $params, $item ) {
	// Check if the time is later than 14:00
	if( date( 'H' ) >= 14 ) {
		$min_date = 2;
	} else {
		$min_date = 1;
	}
	$params[] = '"minDate" : ' . $min_date;
	return $params;
}
add_filter( 'pewc_filter_date_field_params', 'prefix_date_field_params_after_time', 10, 2 );