using System;

using System.Globalization;

​

public class Program

{

    public static void Main()

    {

        var texto = "20250830";

        var provider = new CultureInfo("pt-BR");

        var format = "yyyyMMdd";

        //DateTime.TryParseExact(texto, "yyyyMMdd", provider, System.Globalization.DateTimeStyles.AllowWhiteSpaces |System.Globalization.DateTimeStyles.AdjustToUniversal, out DateTime datahora);

        var data = DateTime.ParseExact(texto, format, provider);

        Console.WriteLine(data);

    }

}