C# - Gets the calendarweek dependent on the current culture

// using System.Globalization;

/// <summary>
/// Gets the calendarweek.
/// </summary>
/// <param name="datetime">The datetime.</param>
/// <returns>the calendarweek</returns>
private static int GetCalendarweek(DateTime datetime)
{
    CultureInfo culture = CultureInfo.CurrentCulture;
    int calendarweek = culture.Calendar.GetWeekOfYear(datetime, CalendarWeekRule.FirstFourDayWeek, DayOfWeek.Monday);
    return calendarweek;
}