Calendar popup for form input that will work with utf-8 - responsive design

We are doing a web site in ASP Classic / HTML and have always use NlsCalendar Professional for our popup calendar form input for date fields. We are doing this site in utf-8 - Responsive design and the control is not behaving with the utf-8 and is not set up for responsive. Does anyone know of a simple calendar popup control that will work in Responsive design with utf-8 or know of a way to convert NlsCalendar to work properly - or do you have a control you have built that you would be willing to sell a copy at reasonable price. Thanks