How do you determine Daylight Savings Time in VBA?

Question

What function will let us know whether a date in VBA is in DST or not?

Answer 1

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.

Pearson's site

Answer 2

I found this to be some very interesting information on DST and Time Zones under VBA.