Our client bought Order Delivery Date Magento 2 Module. Thanks for the good module!
Our QA partner found that the delivery date calendar on checkout reacts to the client time on his PC. So it is currently possible for a customer to set his computer time for 2 hours back and place an order for the next day delivery.
To fix this issue to let Magento calendar use the timezone (as its config http://www.awesomescreenshot.com/09b6b4cbf5 ), could you please try to replace 2 js files of Magento by the attachments?the paths are:
If you have any further question, please feel free to contact us.