計算特定月份的天數

出自ProgWiki

目錄 1 用途 2 MS-SQL預存函數版本 3 C＃版本 4 VB6版本 5 VB.NET版本 6 JavaScript版本 7 其他

用途

• 以年份與月份的數值，計算出該月的總天數。

（閏年規則，四年一閏，百年不閏，四百年再閏）

MS-SQL預存函數版本

SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
 
CREATE FUNCTION [dbo].[GetDaysCount]
(
	@theYear AS INT,
	@theMonth AS INT;
)
RETURNS INT
AS
BEGIN
	DECLARE @theDays AS INT;
 
	IF (@theMonth=2) 
		BEGIN
			IF (((@theYear % 4 = 0) and (@theYear % 100 <> 0)) or (@theYear % 400 = 0))
				SET @theDays = 29
			ELSE
				SET @theDays = 28
		END
	ELSE
		BEGIN
			SELECT @theDays = CASE
				WHEN (@theMonth in (1,3,5,7,8,10,12))THEN
					31
				ELSE
					30
				END;
		END
 
	RETURN @theDays
END

C＃版本

public class DateHelper
{
	public static int GetDaysCount(int theYear, int theMonth)
	{
		int	theDays;
 
		//計算該月天數
		switch (theMonth)
		{
			//31 day
			case 1:		case 3:		case 5:		case 7:
			case 8:		case 10:	case 12:
				theDays = 31;
				break;
			//28 or 29 day
			case 2:
				theDays = 28;
				if (((theYear % 4 == 0) && (theYear % 100 != 0)) || (theYear % 400 == 0))
					theDays = 29;
				break;
			//30 day
			default:
				theDays = 30;
				break;
		}
		return theDays;
	}
}

VB6版本

Public Function GetDaysCount(theYear as Integer, theMonth as Integer) as Integer
	'計算該月天數
	Select Case theMonth
		'31 day
		case 1, 3, 5, 7, 8, 10, 12
			GetDaysCount = 31
 
		'28 or 29 day
		case 2
			if (((theYear % 4 = 0) and (theYear mod 100 <> 0)) or (theYear mod 400 = 0)) Then
				GetDaysCount = 29
			Else
				GetDaysCount = 28
			End If
 
		'30 day
		Case Else
			GetDaysCount = 30
 
	End Select
End Function

VB.NET版本

Public Class DateHelper
	Public Shared Function GetDaysCount(ByVal theYear As Integer, ByVal theMonth As Integer) As Integer
		Dim theDays As Integer
 
		'計算該月天數
		Select Case theMonth
			'31 day
			Case 1, 3, 5, 7, 8, 10, 12
				theDays = 31
				Exit Select
			'28 or 29 day
			Case 2
 
				theDays = 28
				If ((theYear Mod 4 = 0) AndAlso (theYear Mod 100 <> 0)) OrElse (theYear Mod 400 = 0) Then
					theDays = 29
				End If
			Exit Select
		'30 day
		Case Else
			theDays = 30
			Exit Select
		End Select
		Return theDays
	End Function
End Class

JavaScript版本

function GetDaysCount(theYear, theMonth)
{
	var theDaysArray1 = new Array(31,28,31,30,31,30,31,31,30,31,30,31);
	var theDaysArray2 = new Array(31,29,31,30,31,30,31,31,30,31,30,31);
	if (((theYear%4 == 0) && (theYear%100 != 0)) || (theYear%400 == 0))
	{
		return theDaysArray2[theMonth];
	}
	else
	{
		return theDaysArray1[theMonth];
	}
}

其他

• 小朱版本（MS-SQL與C#）（利用時間差的算法）