.NET 可以算出農曆嗎?

答案, 還是Yes!!

.NET Framework (2.0以上)的類別庫中有一個TaiwanLunisolarCalendar 類別(參考: http://msdn2.microsoft.com/zh-tw/library/system.globalization.taiwanlunisolarcalendar.aspx)

這個類別的可看性就多囉!

它與一般的西曆及國曆是很不一樣的, 尤其可能有閏月. 要顯示完整的年月日, 至少要用到以下幾個方法:

• GetSexagenaryYear
• GetCelestialStem
• GetTerrestrialBranch
• GetMonth
• GetLeapMonth
• GetDayOfMonth

下列程式是完整的範例:

        Dim cal As New TaiwanLunisolarCalendar()
        Dim now As Date = Date.Now.AddYears(-1)

        Dim 天干 As String = "甲乙丙丁戊己庚辛壬癸"
        Dim 地支 As String = "子丑寅卯辰巳午未申酉戌亥"

        Dim lun60Year As Integer = cal.GetSexagenaryYear(now)
        Dim 天干Year As Integer = cal.GetCelestialStem(lun60Year) - 1
        Dim 地支Year As Integer = cal.GetTerrestrialBranch(lun60Year) - 1

        Dim lunMonth As Integer = cal.GetMonth(now)
        Dim leapMonth As Integer = cal.GetLeapMonth(cal.GetYear(now))

        If leapMonth > 0 AndAlso lunMonth >= leapMonth Then
            lunMonth -= 1
        End If
        Dim lunDay As Integer = cal.GetDayOfMonth(now)

        MessageBox.Show(String.Format("農曆:{0}年{1}月{2}日", _
           天干(天干Year) & 地支(地支Year), lunMonth, lunDay))

                TaiwanLunisolarCalendar cal =new TaiwanLunisolarCalendar()  ;
                DateTime now  = DateTime.Now.AddYears(-1)  ;
      
                String 天干= "0甲乙丙丁戊己庚辛壬癸"  ;
                String 地支= "0子丑寅卯辰巳午未申酉戌亥"  ;
                  
                int lun60Year = cal.GetSexagenaryYear(now)  ;
                int 天干Year = cal.GetCelestialStem(lun60Year)  ;
                int 地支Year  = cal.GetTerrestrialBranch(lun60Year)   ;
                  
                int lunMonth = cal.GetMonth(now)  ;
                int leapMonth = cal.GetLeapMonth(cal.GetYear(now))  ;
                  
                if (leapMonth > 0 && lunMonth >= leapMonth ) 
                {
                    lunMonth -= 1  ;
                }
                int lunDay = cal.GetDayOfMonth(now)  ;
                  
                MessageBox.Show(String.Format("農曆:{0}年{1}月{2}日",
                   天干[天干Year].ToString() + 地支[地支Year].ToString(), lunMonth, lunDay));

以今天的日期(AddYears(-1))來執行, 得到的結果會是(去年的今天):
農曆:丁亥年2月2日