public DayOfWeek GetDayOfWeekFromLocalizedDayName(string weekDayName, CultureInfo culture = null)
        {
            if (culture == null)
            {
                culture = CultureInfo.CurrentCulture;
            }

            int dayOfWeek = Array.IndexOf(culture.DateTimeFormat.DayNames.Select(x => x.ToLower()).ToArray(), weekDayName.ToLower());
            return (DayOfWeek)dayOfWeek;
        }

DayOfWeek dayOfWeekRu = GetDayOfWeekFromLocalizedDayName("Среда");
                DayOfWeek dayOfWeekDe = GetDayOfWeekFromLocalizedDayName("Mittwoch", new CultureInfo("de-DE"));
                DayOfWeek dayOfWeekIt = GetDayOfWeekFromLocalizedDayName("mercoledì", new CultureInfo("it-it"));
                DayOfWeek dayOfWeekPt = GetDayOfWeekFromLocalizedDayName("quarta-feira", new CultureInfo("pt-BR"));