This is a .Net standard 2.0 class library that you can reference into your .Net Framework or .Net Core app. Please take a look at .Net platforms link for compatibilty and support. The library containt a couple of converter extension methods which you can call in your code for converting different Calendar dates for instance Gregorian date to persian, Please take a look at the Converter.cs for more info.
You can easily clone the project and reference it into your app or you can directly download it in your VS using Nuget Package Manager.
Link of the package: https://www.nuget.org/packages/Date_Converter/