public sealed class HistoricalVersionDescription 

public HistoricalVersion CreateHistoricalVersion(Geodatabase geodatabase, string versionName)
{
    using (VersionManager versionManager = geodatabase.GetVersionManager())
    {
        HistoricalVersionDescription historicalVersionDescription = new HistoricalVersionDescription(versionName, DateTime.Now);
        HistoricalVersion historicalVersion = versionManager.CreateHistoricalVersion(historicalVersionDescription);

        return historicalVersion;
    }
}