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;
  }
}