使用 DatePart() 的 ISO8601 周数不正确
Incorrect ISO8601 Week Number using DatePart()
我的 class 中有以下 Sub。我没有错误，但结果不符合 ISO-8601 标准
Private Sub calculateAllProperties(ByVal dt As Date)
Select Case dt.DayOfWeek
Case DayOfWeek.Monday
m_CurrentWeekStartDate = dt
Case DayOfWeek.Tuesday
m_CurrentWeekStartDate = DateAdd(DateInterval.Day, -1, dt)
Case DayOfWeek.Wednesday
m_CurrentWeekStartDate = DateAdd(DateInterval.Day, -2, dt)
Case DayOfWeek.Thursday
m_CurrentWeekStartDate = DateAdd(DateInterval.Day, -3, dt)
Case DayOfWeek.Friday
m_CurrentWeekStartDate = DateAdd(DateInterval.Day, -4, dt)
Case DayOfWeek.Saturday
m_CurrentWeekStartDate = DateAdd(DateInterval.Day, -5, dt)
Case DayOfWeek.Sunday
m_CurrentWeekStartDate = DateAdd(DateInterval.Day, -6, dt)
End Select
'Now we have our start point of m_CurrentWeekStartDate we can calculate all other properties.
m_CurrentWeekStartYear = DatePart(DateInterval.Year, m_CurrentWeekStartDate)
m_CurrentWeekNo = DatePart(DateInterval.WeekOfYear, m_CurrentWeekStartDate, Microsoft.VisualBasic.FirstDayOfWeek.Monday, FirstWeekOfYear.FirstFourDays)
m_CurrentWeekNoYear = CurrentWeekNo.ToString("D2") & "-" & CurrentWeekStartYear.ToString
m_CurrentYearWeekNo = CurrentWeekStartYear.ToString & "-" & CurrentWeekNo.ToString("D2")
m_PreviousWeekStartDate = DateAdd(DateInterval.Day, -7, m_CurrentWeekStartDate)
m_PreviousWeekStartYear = DatePart(DateInterval.Year, m_PreviousWeekStartDate)
m_PreviousWeekNo = DatePart(DateInterval.WeekOfYear, m_PreviousWeekStartDate, Microsoft.VisualBasic.FirstDayOfWeek.Monday, FirstWeekOfYear.FirstFourDays)
m_PreviousWeekNoYear = PreviousWeekNo.ToString("D2") & "-" & PreviousWeekStartYear.ToString
m_PreviousYearWeekNo = PreviousWeekStartYear.ToString & "-" & PreviousWeekNo.ToString("D2")
End Sub
给定日期 dt
从 m_CurrentWeekNoYear 返回值的一些示例
- 20/07/2015 -> 30-2015 正确
- 09/03/2015 -> 11-2015 正确
- 29/12/2014 -> 53-2014 不正确应该是 01-2015... 使用 02/01/2015
还给了53-2014
- 05/01/2015 -> 01-2015 不正确应该是 02-2015...使用 09/01/2015 也给了 01-2015
- 30/12/2013 -> 53-2013 不正确应该是 01-2014...使用 04/01/2014 也给出了 53-2013
- 06/01/2014 -> 02-2014 正确
然后当我到了实际有 53 周的一年时，它起作用了。
- 28/12/2009 -> 53-2009 正确
- 04/01/2010 -> 01-2010 正确
有没有我哪里出错的想法？
使用 DateAdd 和 DatePart 在这类事情上是出了名的糟糕，但问题是 .NET 计算周数的方式存在（错误）不一致。
查看此页面了解更多信息ISO 8601 Week of Year format in Microsoft .Net
"Specifically ISO 8601 always has 7 day weeks. If the first partial week of a year doesn't contain Thursday, then it is counted as the last week of the previous year. Likewise, if the last week of the previous year doesn't contain Thursday then its[sic] treated like the first week of the next year. GetWeekOfYear() has the first behavior, but not the second"
这是我编写的一些代码，用于根据定义获取 ISO 8601 周数：
"Week number according to the ISO-8601 standard, weeks starting on Monday. The first week of the year is the week that contains that year's first Thursday (='First 4-day week'). The highest week number in a year is either 52 or 53."
''' <summary>
''' Finds the ISO 8601 Week Number based on a given date
''' </summary>
''' <param name="dateValue"></param>
''' <returns></returns>
''' <remarks>ISO 8601 Specifies Monday as the First Day of the week and week one defined as the First Four Day Week</remarks>
Public Shared Function GetIso8601WeekOfYear(ByVal dateValue As DateTime) As Integer
Return GetWeekOfYear(dateValue, DayOfWeek.Sunday, CalendarWeekRule.FirstFourDayWeek)
End Function
它使用以下更通用的方法使用 ISO 标准的细节来查找一年中的第几周：
'Need a calendar - Culture's irrelevent since we specify start day of week
Private Shared cal As Calendar = CultureInfo.InvariantCulture.Calendar
''' <summary>
''' Returns the week number of the year based on the Last Day of the Week and the Week One Rule
''' </summary>
''' <param name="dateValue">The date to find the week number for</param>
''' <param name="lastDayOfWeek">The last day of the week</param>
''' <param name="rule">The Definition of Week One</param>
''' <returns>An integer specifying the week number in the year</returns>
''' <remarks></remarks>
Public Shared Function GetWeekOfYear(ByVal dateValue As DateTime, ByVal lastDayOfWeek As DayOfWeek, ByVal rule As CalendarWeekRule) As Integer
'There is a bug in the .NET framework where some dates at the end of the year return the incorrect week number so to find the correct value we need to cheat.
'Find the DayOfWeek that represents the first day based on the last day
Dim firstDayOfWeek As DayOfWeek = lastDayOfWeek.Increment
'Find the date of the last day of the week, this ensures that we get the correct week number value
dateValue = GetWeekendingDate(dateValue, lastDayOfWeek)
'Return the value of the week for the last day of the week
Return cal.GetWeekOfYear(dateValue, rule, firstDayOfWeek)
End Function
''' <summary>
''' Finds the week ending date for a specified date value
''' </summary>
''' <param name="dateValue">The date to find the week ending date for</param>
''' <param name="lastDayOfWeek">The last day of the week</param>
''' <returns>A date value that is the last day of the week that contains the specified dateValue</returns>
''' <remarks></remarks>
Public Shared Function GetWeekendingDate(ByVal dateValue As DateTime, ByVal lastDayOfWeek As DayOfWeek) As DateTime
'Find out how many days difference from the date we are testing to the end of the week
Dim dayOffset As Integer = lastDayOfWeek - cal.GetDayOfWeek(dateValue)
If dayOffset < 0 Then dayOffset += 7
'Add days to the test date so that it is the last day of the week
Return dateValue.AddDays(dayOffset)
End Function
此代码使用此扩展方法，该方法可快速查找一周中的下一天：
<Extension()>
Public Function Increment(ByVal aDay As DayOfWeek) As DayOfWeek
Select Case aDay
Case DayOfWeek.Sunday : Return DayOfWeek.Monday
Case DayOfWeek.Monday : Return DayOfWeek.Tuesday
Case DayOfWeek.Tuesday : Return DayOfWeek.Wednesday
Case DayOfWeek.Wednesday : Return DayOfWeek.Thursday
Case DayOfWeek.Thursday : Return DayOfWeek.Friday
Case DayOfWeek.Friday : Return DayOfWeek.Saturday
Case DayOfWeek.Saturday : Return DayOfWeek.Sunday
Case Else : Return Nothing
End Select
End Function
我用这个测试了你的测试用例并得到了以下结果：
Debug.WriteLine(GetIso8601WeekOfYear(Date.Parse("20/07/2015"))) '30
Debug.WriteLine(GetIso8601WeekOfYear(Date.Parse("09/03/2015"))) '11
Debug.WriteLine(GetIso8601WeekOfYear(Date.Parse("29/12/2014"))) '1
Debug.WriteLine(GetIso8601WeekOfYear(Date.Parse("05/01/2015"))) '2
Debug.WriteLine(GetIso8601WeekOfYear(Date.Parse("30/12/2013"))) '1
Debug.WriteLine(GetIso8601WeekOfYear(Date.Parse("06/01/2014"))) '2
下面是 DatePart 函数中 error 的简单解决方法：
Week = DatePart("ww", myDate, vbMonday, vbFirstFourDays)
If Week = 53 And DatePart("ww", DateAdd("d", 7, myDate), vbMonday, vbFirstFourDays) = 2 Then
Week = 1
End If
我的 class 中有以下 Sub。我没有错误，但结果不符合 ISO-8601 标准
Private Sub calculateAllProperties(ByVal dt As Date)
Select Case dt.DayOfWeek
Case DayOfWeek.Monday
m_CurrentWeekStartDate = dt
Case DayOfWeek.Tuesday
m_CurrentWeekStartDate = DateAdd(DateInterval.Day, -1, dt)
Case DayOfWeek.Wednesday
m_CurrentWeekStartDate = DateAdd(DateInterval.Day, -2, dt)
Case DayOfWeek.Thursday
m_CurrentWeekStartDate = DateAdd(DateInterval.Day, -3, dt)
Case DayOfWeek.Friday
m_CurrentWeekStartDate = DateAdd(DateInterval.Day, -4, dt)
Case DayOfWeek.Saturday
m_CurrentWeekStartDate = DateAdd(DateInterval.Day, -5, dt)
Case DayOfWeek.Sunday
m_CurrentWeekStartDate = DateAdd(DateInterval.Day, -6, dt)
End Select
'Now we have our start point of m_CurrentWeekStartDate we can calculate all other properties.
m_CurrentWeekStartYear = DatePart(DateInterval.Year, m_CurrentWeekStartDate)
m_CurrentWeekNo = DatePart(DateInterval.WeekOfYear, m_CurrentWeekStartDate, Microsoft.VisualBasic.FirstDayOfWeek.Monday, FirstWeekOfYear.FirstFourDays)
m_CurrentWeekNoYear = CurrentWeekNo.ToString("D2") & "-" & CurrentWeekStartYear.ToString
m_CurrentYearWeekNo = CurrentWeekStartYear.ToString & "-" & CurrentWeekNo.ToString("D2")
m_PreviousWeekStartDate = DateAdd(DateInterval.Day, -7, m_CurrentWeekStartDate)
m_PreviousWeekStartYear = DatePart(DateInterval.Year, m_PreviousWeekStartDate)
m_PreviousWeekNo = DatePart(DateInterval.WeekOfYear, m_PreviousWeekStartDate, Microsoft.VisualBasic.FirstDayOfWeek.Monday, FirstWeekOfYear.FirstFourDays)
m_PreviousWeekNoYear = PreviousWeekNo.ToString("D2") & "-" & PreviousWeekStartYear.ToString
m_PreviousYearWeekNo = PreviousWeekStartYear.ToString & "-" & PreviousWeekNo.ToString("D2")
End Sub
给定日期 dt
从 m_CurrentWeekNoYear 返回值的一些示例- 20/07/2015 -> 30-2015 正确
- 09/03/2015 -> 11-2015 正确
- 29/12/2014 -> 53-2014 不正确应该是 01-2015... 使用 02/01/2015 还给了53-2014
- 05/01/2015 -> 01-2015 不正确应该是 02-2015...使用 09/01/2015 也给了 01-2015
- 30/12/2013 -> 53-2013 不正确应该是 01-2014...使用 04/01/2014 也给出了 53-2013
- 06/01/2014 -> 02-2014 正确
然后当我到了实际有 53 周的一年时，它起作用了。
- 28/12/2009 -> 53-2009 正确
- 04/01/2010 -> 01-2010 正确
有没有我哪里出错的想法？
使用 DateAdd 和 DatePart 在这类事情上是出了名的糟糕，但问题是 .NET 计算周数的方式存在（错误）不一致。
查看此页面了解更多信息ISO 8601 Week of Year format in Microsoft .Net
"Specifically ISO 8601 always has 7 day weeks. If the first partial week of a year doesn't contain Thursday, then it is counted as the last week of the previous year. Likewise, if the last week of the previous year doesn't contain Thursday then its[sic] treated like the first week of the next year. GetWeekOfYear() has the first behavior, but not the second"
这是我编写的一些代码，用于根据定义获取 ISO 8601 周数：
"Week number according to the ISO-8601 standard, weeks starting on Monday. The first week of the year is the week that contains that year's first Thursday (='First 4-day week'). The highest week number in a year is either 52 or 53."
''' <summary>
''' Finds the ISO 8601 Week Number based on a given date
''' </summary>
''' <param name="dateValue"></param>
''' <returns></returns>
''' <remarks>ISO 8601 Specifies Monday as the First Day of the week and week one defined as the First Four Day Week</remarks>
Public Shared Function GetIso8601WeekOfYear(ByVal dateValue As DateTime) As Integer
Return GetWeekOfYear(dateValue, DayOfWeek.Sunday, CalendarWeekRule.FirstFourDayWeek)
End Function
它使用以下更通用的方法使用 ISO 标准的细节来查找一年中的第几周：
'Need a calendar - Culture's irrelevent since we specify start day of week
Private Shared cal As Calendar = CultureInfo.InvariantCulture.Calendar
''' <summary>
''' Returns the week number of the year based on the Last Day of the Week and the Week One Rule
''' </summary>
''' <param name="dateValue">The date to find the week number for</param>
''' <param name="lastDayOfWeek">The last day of the week</param>
''' <param name="rule">The Definition of Week One</param>
''' <returns>An integer specifying the week number in the year</returns>
''' <remarks></remarks>
Public Shared Function GetWeekOfYear(ByVal dateValue As DateTime, ByVal lastDayOfWeek As DayOfWeek, ByVal rule As CalendarWeekRule) As Integer
'There is a bug in the .NET framework where some dates at the end of the year return the incorrect week number so to find the correct value we need to cheat.
'Find the DayOfWeek that represents the first day based on the last day
Dim firstDayOfWeek As DayOfWeek = lastDayOfWeek.Increment
'Find the date of the last day of the week, this ensures that we get the correct week number value
dateValue = GetWeekendingDate(dateValue, lastDayOfWeek)
'Return the value of the week for the last day of the week
Return cal.GetWeekOfYear(dateValue, rule, firstDayOfWeek)
End Function
''' <summary>
''' Finds the week ending date for a specified date value
''' </summary>
''' <param name="dateValue">The date to find the week ending date for</param>
''' <param name="lastDayOfWeek">The last day of the week</param>
''' <returns>A date value that is the last day of the week that contains the specified dateValue</returns>
''' <remarks></remarks>
Public Shared Function GetWeekendingDate(ByVal dateValue As DateTime, ByVal lastDayOfWeek As DayOfWeek) As DateTime
'Find out how many days difference from the date we are testing to the end of the week
Dim dayOffset As Integer = lastDayOfWeek - cal.GetDayOfWeek(dateValue)
If dayOffset < 0 Then dayOffset += 7
'Add days to the test date so that it is the last day of the week
Return dateValue.AddDays(dayOffset)
End Function
此代码使用此扩展方法，该方法可快速查找一周中的下一天：
<Extension()>
Public Function Increment(ByVal aDay As DayOfWeek) As DayOfWeek
Select Case aDay
Case DayOfWeek.Sunday : Return DayOfWeek.Monday
Case DayOfWeek.Monday : Return DayOfWeek.Tuesday
Case DayOfWeek.Tuesday : Return DayOfWeek.Wednesday
Case DayOfWeek.Wednesday : Return DayOfWeek.Thursday
Case DayOfWeek.Thursday : Return DayOfWeek.Friday
Case DayOfWeek.Friday : Return DayOfWeek.Saturday
Case DayOfWeek.Saturday : Return DayOfWeek.Sunday
Case Else : Return Nothing
End Select
End Function
我用这个测试了你的测试用例并得到了以下结果：
Debug.WriteLine(GetIso8601WeekOfYear(Date.Parse("20/07/2015"))) '30
Debug.WriteLine(GetIso8601WeekOfYear(Date.Parse("09/03/2015"))) '11
Debug.WriteLine(GetIso8601WeekOfYear(Date.Parse("29/12/2014"))) '1
Debug.WriteLine(GetIso8601WeekOfYear(Date.Parse("05/01/2015"))) '2
Debug.WriteLine(GetIso8601WeekOfYear(Date.Parse("30/12/2013"))) '1
Debug.WriteLine(GetIso8601WeekOfYear(Date.Parse("06/01/2014"))) '2
下面是 DatePart 函数中 error 的简单解决方法：
Week = DatePart("ww", myDate, vbMonday, vbFirstFourDays)
If Week = 53 And DatePart("ww", DateAdd("d", 7, myDate), vbMonday, vbFirstFourDays) = 2 Then
Week = 1
End If