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! --------------------------------------------------------------------------------------

Module modDateTime

	! 階段數常數
	Integer, Parameter :: SC_Year = 1
	Integer, Parameter :: SC_Month = 12
	Integer, Parameter :: SC_TenDays = 36 ! 旬
	Integer, Parameter :: SC_Day = 365
	Integer, Parameter :: SC_Days = 366

Contains

	Integer Function GetStageDays(vYear, vIndex, StageCount)
		Integer :: vYear, vIndex, StageCount
		Logical :: bAddDay
		Integer :: nDays
		
		bAddDay = .False.
		
		Select Case (StageCount)
		Case (SC_Year)
			nDays = 365
			bAddDay = .True.
		Case (SC_Month)
			Select Case (vIndex)
			Case (2)
				nDays = 28
				bAddDay = .True.
			Case (4, 6, 9, 11)
				nDays = 30
			Case DEFAULT
				nDays = 31
			End Select
		Case (SC_TenDays)
			Select Case (vIndex)
			Case (6)
				nDays = 8
				bAddDay = .True.
			Case (3, 9, 15, 21, 24, 30, 36)
				nDays = 11
			Case DEFAULT
				nDays = 10
			End Select
		Case (SC_Day, SC_Days)
			nDays = 1
		End Select
		
		If (bAddDay) Then
			If (IsLeapYear(vYear)) Then
				nDays = nDays + 1
			End If
		End If
		GetStageDays = nDays
	End Function
	
	Logical Function IsLeapYear(vYear)
	! 是否為閏年
		Integer :: vYear
		Logical :: bLeapYear
		
		bLeapYear = .False.
		If (Mod(vYear, 4) == 0) Then
			bLeapYear = .True.
			If (Mod(vYear, 100) == 0) Then
				bLeapYear = .False.
				If (Mod(vYear, 400) == 0) Then
					bLeapYear = .True.
				End If
			End If				
		End If
		
		IsLeapYear = bLeapYear		
	End Function

	Integer Function GetStageIndex(vYear, vMonth, vDay, StageCount, bNoLeapDay)
		Integer :: vYear, vMonth, vDay, StageCount
		Integer :: nIndex, nMonth, i
		Logical :: bNoLeapDay, pNoLeapDay
		Optional :: bNoLeapDay

      If (Present(bNoLeapDay)) Then
			pNoLeapDay = bNoLeapDay
		Else
		   pNoLeapDay = .False. ! 預設有閏日
		End If      

		Select Case (StageCount)
		Case (SC_Year)
			nIndex = 1
		Case (SC_Month)
			nIndex = vMonth
		Case (SC_TenDays)
			nMonth = (vMonth - 1) * 3
   
			If (vDay .le. 10) Then
				nIndex = 1
			Else If (vDay .le. 20) Then
				nIndex = 2
			Else
				nIndex = 3
			End If
			nIndex = nIndex + nMonth
		Case (SC_Day, SC_Days)
			nIndex = vDay
			Do i = 1, vMonth - 1
				nIndex = nIndex + GetStageDays(vYear, i, SC_Month)
			End Do
			If (pNoLeapDay .And. IsLeapYear(vYear) .And. vMonth > 2) Then
			   nIndex = nIndex - 1
			End If
		End Select

		GetStageIndex = nIndex

	End Function

	Subroutine DateAdd(vYear, vMonth, vDay, addDay)
		Integer :: vYear, vMonth, vDay, addDay
		Integer :: nDay

		vDay = vDay + addDay
		nDay = GetMonthDays(vYear, vMonth)
		Do While (vDay > nDay)
			vDay = vDay - nDay
			vMonth = vMonth + 1
			If (vMonth > SC_Month) Then
				vMonth = 1
				vYear = vYear + 1
			End If
			nDay = GetMonthDays(vYear, vMonth)
		End Do

	End Subroutine

	Integer Function GetMonthDays(vYear, vMonth)
		Integer :: vYear, vMonth

		Select Case (vMonth)
		Case (1, 3, 5, 7, 8, 10, 12)
			GetMonthDays = 31
		Case (4, 6, 9, 11)
			GetMonthDays = 30
		Case (2)
			If (IsLeapYear(vYear)) Then
				GetMonthDays = 29
			Else
				GetMonthDays = 28
			End If
		End Select

	End Function

End Module