Is Daypilot have an on-premise solution? We are looking out for a third party tool that can integrate with our software and SQL Server 2012 . We will need the calendar events to write into our database so that they can be used in our software
Yes, this is how it works - it's a library that you can use in your own application. It will work with your database just fine.
See also the ASP.NET tutorials to see example applications that access data stored in an SQL Server database: