Creating reports and dashboards | Stimulsoft community forum
Reporting tool and data analytics tools for creating reports and dashboards in ASP.NET, ASP.NET MVC, .NET Core, Blazor, Angular, PHP, Python, WPF, JavaScript, and Java applications.
Found the solution, setting the field to datetime it was parsed in from json as string. And you also need to use "..." and not '...' as first parameter of Format()