如何确定VBA中的夏令时？

在VBA中，确定夏令时可以通过以下方法：

使用TimeValue函数和DateValue函数：

Sub CheckDaylightSavingTime()
    Dim currentDate As Date
    Dim currentTime As Date
    Dim isDaylightSavingTime As Boolean

    currentDate = DateValue("2022-06-01")
    currentTime = TimeValue("12:00:00")

    isDaylightSavingTime = IsDaylightSavingTime(currentDate, currentTime)

    If isDaylightSavingTime Then
        MsgBox "夏令时生效中"
    Else
        MsgBox "夏令时未生效"
    End If
End Sub

Function IsDaylightSavingTime(ByVal dateValue As Date, ByVal timeValue As Date) As Boolean
    Dim baseDate As Date
    Dim baseTime As Date
    Dim baseDateTime As Date
    Dim testDateTime As Date

    baseDate = DateSerial(Year(dateValue), Month(dateValue), 1)
    baseTime = TimeSerial(Hour(timeValue), Minute(timeValue), Second(timeValue))
    baseDateTime = DateValue(baseDate) + baseTime

    testDateTime = baseDateTime - 60 ' 减去60分钟

    If Hour(testDateTime) = Hour(baseDateTime) Then
        IsDaylightSavingTime = True
    Else
        IsDaylightSavingTime = False
    End If
End Function

使用GetTimeZoneInformationAPI函数：

Sub CheckDaylightSavingTime()
    Dim tzi As TIME_ZONE_INFORMATION
    Dim result As Long

    result = GetTimeZoneInformation(tzi)

    If result = TIME_ZONE_ID_DAYLIGHT Then
        MsgBox "夏令时生效中"
    Else
        MsgBox "夏令时未生效"
    End If
End Sub

Private Type TIME_ZONE_INFORMATION
    Bias As Long
    StandardName(31) As Integer
    StandardDate As SYSTEMTIME
    StandardBias As Long
    DaylightName(31) As Integer
    DaylightDate As SYSTEMTIME
    DaylightBias As Long
End Type

Private Type SYSTEMTIME
    wYear As Integer
    wMonth As Integer
    wDayOfWeek As Integer
    wDay As Integer
    wHour As Integer
    wMinute As Integer
    wSecond As Integer
    wMilliseconds As Integer
End Type

Private Declare PtrSafe Function GetTimeZoneInformation Lib "kernel32" (lpTimeZoneInformation As TIME_ZONE_INFORMATION) As Long

Private Const TIME_ZONE_ID_UNKNOWN As Long = 0
Private Const TIME_ZONE_ID_STANDARD As Long = 1
Private Const TIME_ZONE_ID_DAYLIGHT As Long = 2

这两种方法都可以用来确定VBA中的夏令时。第一种方法使用TimeValue和DateValue函数来获取当前日期和时间，然后通过比较当前时间和减去60分钟后的时间来判断是否处于夏令时。第二种方法使用GetTimeZoneInformationAPI函数来获取时区信息，然后判断是否处于夏令时。