How do you determine Daylight Savings Time in VBA?
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02-07-2019 - |
Question
What function will let us know whether a date in VBA is in DST or not?
Solution
For non-current dates (DST 2007+):
First, you need a function to find the number of specific weekdays in a month:
Public Function NDow(Y As Integer, M As Integer, _
N As Integer, DOW As Integer) As Date
' Returns Date of Nth Day of the Week in Month
NDow = DateSerial(Y, M, (8 - Weekday(DateSerial(Y, M, 1), _
(DOW + 1) Mod 8)) + ((N - 1) * 7))
End Function
Then, you can check for the DST day versus the following function calls:
Fall: NDow(Year(newdate), 11, 1, 1)
Spring: NDow(Year(newdate), 3, 2, 1)
For the current date:
Call the Windows API function GetTimeZoneInformation, and it will return an enum (integer) with the status.
I got the code for this from Chip Pearson's great Excel site.
OTHER TIPS
For anyone wondering how to account for daylight saving time in Europe (central europe time), I modified the script from Chip Pearson. The last sunday of March (2 AM to 3 AM) and October (3 AM to 2 AM) are the days when the hour switching occurs.
Following code is the click event of a button in Excel:
Dim dates As String
dates = "A1:A20"
For Each c In Worksheets("Sheet1").Range(dates).Cells
If (IsDateWithinDST(c.Value)) Then
c.Value = DateAdd("h", 1, c.Value)
End If
Next
The module containing the necessary methods are to be found here.