<input class="button" type="submit" value="<?php _e('Оплатить', 'inte');?>" style="background-color: #ef8989">
setTimeout(function(){
$('button').trigger('click');
}, 1000);
<input id="datepicker" class="button" type="submit" value="<?php _e('Оплатить', 'inter');?>" style="background-color: #ef8989">
<?php echo $cancel_url;?>
</form>
<script>
setTimeout(function(){
$('#datepicker').trigger('click');
}, 1000);
</script>