こんなのあったのか＞＜；

EastAsianLunisolarCalendar.ToDateTime(Int32, Int32, Int32, Int32, Int32, Int32, Int32, Int32) Method (System.Globalization) | Microsoft Docs https://docs.microsoft.com/en-us/dotnet/api/system.globalization.eastasianlunisolarcalendar.todatetime